Key Lime Mojito Cake with Fresh Mint and Citrus Glaze

Key lime mojito cake is a soft lime cake finished with a mint-infused syrup and a tangy citrus glaze. It brings the bright lime and fresh mint notes of a mojito to an easy sheet cake, with no cocktail shaker or special pan required.

Ingredients

2 cups (250 g) all-purpose flour, spooned into the measuring cup and leveled
2 teaspoons (8 g) baking powder
½ teaspoon (2.5 g) baking soda
½ teaspoon (3 g) fine salt
¾ cup (170 g) unsalted butter, softened
1¼ cups (250 g) granulated sugar
3 large eggs, at room temperature (about 150 g without shells)
2 tablespoons finely grated lime zest (from about 4 limes)
2 teaspoons (10 ml) vanilla extract
⅓ cup (80 ml) fresh lime juice, divided: ¼ cup (60 ml) for the cake and 1 tablespoon (15 ml) for the mint syrup
¾ cup (180 g) sour cream, at room temperature
½ cup (120 ml) whole milk, at room temperature
½ cup lightly packed fresh mint leaves (about 15 g), plus a few small leaves to garnish
⅓ cup (67 g) granulated sugar, for the mint syrup
⅓ cup (80 ml) water, for the mint syrup
1½ cups (180 g) powdered sugar, for the glaze
1½ to 2 tablespoons (22–30 ml) fresh lime juice, for the glaze
1 tablespoon (15 g) sour cream, for the glaze
Optional: 1 teaspoon (5 ml) white rum in the glaze for a cocktail-inspired note; omit it for an alcohol-free cake

Instructions

Heat the oven to 350°F (175°C). Grease a 9-by-13-inch (23-by-33-cm) baking pan and line the bottom with parchment if you want to lift the cake out easily. Set the butter, eggs, sour cream, and milk out ahead so they are not cold; room-temperature ingredients combine more evenly and help the cake rise consistently.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. In a large bowl, beat the softened butter and 1¼ cups sugar with a hand mixer or stand mixer on medium speed for about 3 minutes, until pale and fluffy. Scrape the bowl once so the butter at the edges is mixed in.
Beat in the eggs one at a time, mixing just until each is incorporated. Add the lime zest and vanilla. In a separate small bowl or measuring jug, stir together the ¼ cup lime juice, ¾ cup sour cream, and milk. The mixture may look slightly curdled from the lime; that is fine once it is added to the batter.
Add about one-third of the flour mixture to the butter mixture and mix on low just until the flour mostly disappears. Add half the sour cream mixture, then another third of the flour, the remaining sour cream mixture, and the last of the flour. Mix only until no dry streaks remain, scraping the bowl as needed. Overmixing can make the cake dense.
Scrape the batter into the prepared pan and smooth the top. Bake for 30–35 minutes, rotating the pan once if your oven browns unevenly. Begin checking at 30 minutes: a wooden pick inserted in the center should come out clean or with a few moist crumbs, and the top should spring back gently. For egg safety, USDA FSIS lists 160°F (71°C) as the safe minimum internal temperature for egg dishes when checked with a food thermometer; a finished cake typically reaches about 200–205°F (93–96°C) in the center. Avoid opening the oven during the first 25 minutes, which can interrupt the rise.
While the cake bakes, make the mint syrup. Put the ⅓ cup sugar and water in a small saucepan and bring to a simmer over medium heat, stirring until the sugar dissolves. Simmer for 1 minute, then remove the pan from the heat, add the mint leaves, and steep for 10 minutes. Strain out the leaves and stir in 1 tablespoon lime juice. Do not boil the mint for a long time, as that can give the syrup a dull or grassy flavor.
Let the baked cake rest in its pan for 10 minutes. Use a skewer to poke holes across the top, spacing them about an inch (2.5 cm) apart. Slowly spoon or brush the mint syrup over the cake, giving it time to soak in rather than pooling in one spot. Leave the cake in the pan and cool completely, about 50 minutes more. The syrup adds moisture and a clear mint aroma; it should not make the crumb soggy when applied gradually.
Whisk the powdered sugar with 1½ tablespoons lime juice and the tablespoon of sour cream. Add more lime juice a teaspoon at a time until the glaze is thick but pourable. Stir in the optional rum, if using. Drizzle over the fully cooled cake and let the glaze set for about 20 minutes. Garnish with a little extra lime zest or a few small mint leaves just before serving, since cut mint can darken as it sits.

Tips

Use fresh lime juice and zest for the cleanest flavor. Bottled juice can work in the glaze in a pinch, but it is usually less fragrant; it will not replace the fresh zest in the cake. Key limes are small and take more effort to juice, so regular Persian limes are a practical substitute with a slightly less floral, still pleasantly tart result.
Measure flour by spooning it into the cup and leveling the top rather than scooping directly from the bag. A packed cup adds too much flour and can make the cake dry. If using a scale, the listed gram amount is the most consistent measure.
Keep the mint syrup warm or at room temperature when you brush it on, and add it in several passes. If it sits on the cake in a puddle, the surface can turn gummy. Strain the syrup well so mint pieces do not interfere with a smooth glaze.
If you do not have sour cream, use the same amount of full-fat plain Greek yogurt in the cake. The crumb may be a little less rich, but it will still be tender. Do not substitute mint extract one-for-one for fresh mint: extracts vary greatly in strength and can taste sharp; if necessary, use only a few drops in the syrup and taste as you go.

Serving Suggestions

Serve the cake at cool room temperature, cut into 12 squares. Its lime and mint flavors are bright but not as sharp as a cocktail, so it pairs well with fresh berries, sliced mango, or a small spoonful of softly whipped cream. For a dessert table, cut it into smaller squares and add a thin lime wheel or a single mint leaf to each piece just before serving; a little garnish is enough because the glaze already brings plenty of citrus.

This is a useful cake for a picnic or gathering because it travels in its baking pan and does not need elaborate decoration. Keep it chilled if the weather is warm, then let it stand for about 20 minutes before serving so the crumb softens and the lime flavor comes forward. The recipe is a mojito-inspired dessert rather than a traditional regional cake, and the fresh mint can be adjusted to suit the people at your table.

Variations

Make cupcakes: Divide the batter among 18 lined standard muffin cups, filling each about two-thirds full. Bake at 350°F (175°C) for roughly 18–22 minutes, checking with a pick and thermometer as described for the cake. Brush each warm cupcake lightly with mint syrup and glaze once cool. Since cupcakes have more exposed surface area, start with less syrup and add only enough to moisten without making the tops sticky.

Use a coconut finish: Replace the whole milk with the same amount of canned coconut milk and scatter ⅓ cup (25 g) unsweetened shredded coconut over the glaze before it sets. Coconut adds a mellow, tropical note and soft texture; it does not replace the lime or mint, so keep those amounts the same.

Make it alcohol-free: The cake is alcohol-free if you leave the optional rum out of the glaze. To make the glaze more aromatic without it, add an extra ½ teaspoon lime zest. For a stronger mint flavor, steep a few extra mint leaves in the syrup rather than adding a large amount of mint extract, which can overwhelm the citrus.

Try a two-layer cake: The batter can be divided between two greased and parchment-lined 8-inch (20-cm) round pans. Start checking after about 24 minutes; the exact time depends on pan material and oven. Cool the layers completely before brushing with syrup, then use a little less syrup on the cut sides if you are stacking them so the layers remain easy to handle. Use a thin layer of glaze between or over the layers, or keep the glaze on top for simpler serving.

Storage and Reheating

Because the cake has a sour-cream glaze, refrigerate it within 2 hours of baking or serving. Cover the pan tightly or transfer slices to an airtight container; the cake keeps well in the refrigerator for 3–4 days. The crumb firms when cold, so set a portion on the counter for about 20–30 minutes before eating. There is no need to reheat it, and warming glazed slices can make the topping run.

For longer storage, freeze unglazed, fully cooled slices wrapped individually and placed in a freezer-safe container for up to 2 months. Thaw them overnight in the refrigerator, then glaze after thawing for the neatest finish. If the cake is already glazed, freeze portions on a tray until firm before wrapping; the glaze may look less smooth after thawing, but the cake will still be enjoyable. Do not leave it at room temperature for extended storage.

Frequently Asked Questions

Can I use regular limes instead of key limes?

Yes. Regular Persian limes are easier to find and work well in the cake, syrup, and glaze. Key limes have a smaller, often more floral aroma, so the flavor will be a little different, but the recipe does not require them. Use the same measured juice and zest rather than relying on a specific number of limes, since fruit size and juiciness vary.

Can I make the cake a day ahead?

Yes. Bake it, brush it with the mint syrup, cool it fully, and store it covered in the refrigerator. You can glaze it the day before or wait until the day you plan to serve it; glazing shortly before serving gives the freshest appearance. Keep the cake chilled and follow the two-hour refrigeration guidance after serving.

Why did my cake turn out dense?

The most common causes are too much flour, cold ingredients, or overmixing once the flour is added. Spoon and level the flour, bring the dairy and eggs toward room temperature, and mix the final batter only until the dry streaks disappear. Also check that the baking powder and baking soda are fresh, since old leaveners may not lift the batter properly.

Can I leave out the mint syrup?

You can, but the cake will taste more like a lime cake than a mojito-inspired one and may be slightly less moist. If you skip the syrup, add a little extra lime zest to the glaze and serve the cake with fresh mint on the side. Do not pour plain lime juice over the cake as a direct substitute; it can make isolated spots sharply sour and wet.

How can I tell when the cake is done without drying it out?

Start checking at 30 minutes. The center should spring back lightly, and a skewer should come out clean or with a few moist crumbs rather than raw batter. A food thermometer can confirm the center has passed the USDA FSIS safe minimum for egg dishes; cakes commonly finish well above that minimum. Remove the pan promptly once done, since extra oven time can dry the edges.

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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

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