Mojito Cake Recipe UK: A Zesty Lime, Mint and Rum Bake

This mojito cake is a soft lime sponge flavoured with fresh mint, brushed with a fragrant lime-and-mint syrup and finished with a tangy buttercream. Inspired by the Cuban cocktail, it brings its familiar citrus and mint notes to a celebration cake; the rum is optional, and the recipe works well with UK ingredients and measurements.

Ingredients

250 g (2 cups) self-raising flour
200 g (1 cup) caster sugar
175 g (¾ cup) unsalted butter, softened
3 large eggs, at room temperature
60 ml (¼ cup) whole milk
Finely grated zest of 2 limes, plus 30 ml (2 tbsp) juice
1 tsp (4 g) baking powder
¼ tsp fine salt
2 tbsp (about 3 g) finely chopped fresh mint leaves
For the syrup: 50 g (¼ cup) caster sugar, 60 ml (¼ cup) lime juice, 30 ml (2 tbsp) water, 10 g (about ½ cup loosely packed) fresh mint leaves and 30 ml (2 tbsp) white or golden rum, optional
For the buttercream: 200 g (7 oz) unsalted butter, softened; 300 g (2½ cups) icing sugar, sifted; 15 ml (1 tbsp) lime juice; finely grated zest of 1 lime; and 15–30 ml (1–2 tbsp) rum or milk, as needed
To decorate: 6–8 small mint leaves and 1 lime, cut into thin slices or wedges

Instructions

Prepare the tins and oven. Heat the oven to 350°F (180°C), or 320°F (160°C) for a fan oven. Grease two 20 cm (8-inch) round cake tins and line their bases with baking parchment. Set the butter out ahead of time if it is still firm; softened butter should give slightly when pressed but should not look oily.
Mix the sponge batter. In a large bowl, beat the softened butter and caster sugar for 3–4 minutes, until pale and fluffy. Beat in the eggs one at a time, scraping down the bowl as needed. If the mixture looks slightly curdled, add a spoonful of the measured flour and continue. Stir in the lime zest, lime juice and chopped mint. In a separate bowl, combine the self-raising flour, baking powder and salt. Fold the dry ingredients into the butter mixture in two additions, alternating with the milk. Stop as soon as no dry flour remains; overmixing can make the sponge firm.
Bake the layers. Divide the batter evenly between the tins and level the tops. Bake for 25–28 minutes, swapping the tins between oven shelves after about 18 minutes if your oven heats unevenly. The cakes are ready when they spring back lightly in the centre and a skewer inserted into the middle comes out clean or with a few dry crumbs. Because this is a baked cake containing eggs, ensure the centre reaches at least 160°F (71°C), the USDA FSIS safe minimum for egg dishes. Leave the cakes in their tins for 15 minutes, then turn them out onto a rack and let them cool completely, about 45 minutes.
Make the mint-lime syrup. While the cakes bake, put the syrup sugar, lime juice and water in a small saucepan. Warm over low heat, stirring until the sugar dissolves, then simmer gently for 1 minute. Take the pan off the heat, add the mint leaves and press them gently with the back of a spoon to release their aroma. Let the syrup cool for 15 minutes, then strain out the mint. Stir in the rum, if using, once the syrup is cool. This cake contains optional rum and is intended for adults of legal drinking age; drink responsibly.
Make the buttercream. Beat the softened butter for 2 minutes until smooth. Add the sifted icing sugar in three additions, mixing slowly at first so it does not puff out of the bowl. Beat in the lime zest and lime juice, then add rum or milk a teaspoon at a time until the icing is smooth and spreadable. Taste it before adding all the liquid: the buttercream should hold its shape but still be easy to spread.
Fill and finish the cake. Set one cooled layer on a serving plate. Brush its top with about half of the cooled syrup, letting it soak in rather than pooling around the edge. Spread over roughly one-third of the buttercream. Add the second cake layer, brush its top with the remaining syrup, then spread the rest of the buttercream over the top. You can leave the sides bare for a relaxed finish or use a small offset spatula to spread a thin coat around them. Decorate with mint leaves and lime slices just before serving.

Tips

Measure the flour gently. If using cups, spoon flour into the cup and level it rather than scooping directly from the bag, which can pack in too much. A kitchen scale gives the most consistent sponge, especially when dividing batter between two tins.
Keep the mint fresh and restrained. Use tender leaves and avoid chopping them far in advance, as they can darken. The finely chopped mint in the sponge gives a light herbal note; the syrup supplies more aroma. Thick stems can taste coarse, so pick the leaves from the stems before measuring.
Make it without alcohol. Leave rum out of both syrup and buttercream and use milk in the icing. The cake will still have the lime-and-mint character of a mojito-inspired bake, though it will miss the warm, slightly rounded flavour of rum.
Wait until the layers are cool. Warm sponge melts buttercream and can make it slide. If a layer has a small dome, level it with a serrated knife once cool, then use the trimmed crumbs as a little finishing garnish if desired.

Serving Suggestions

Serve the cake at room temperature, when the buttercream is soft and the lime flavour is easiest to taste. Cut it with a sharp knife, wiping the blade between slices for neat edges. A small mint leaf or slim lime wedge on each piece makes a simple garnish; add these shortly before serving so the leaves stay bright and the cut lime does not dry out.

This is a good choice for afternoon tea, a summer birthday or a dinner-party dessert. Pair it with plain tea, coffee or sparkling water with lime. If serving it after a rich meal, modest slices are satisfying because the citrus syrup and tangy icing give the cake a lively finish. Since the rum is optional but remains in the finished cake when used, let guests know before serving.

Variations

Make a single-layer tray cake: bake the batter in a greased and lined 23 cm (9-inch) square tin. Start checking at 25 minutes; it may need a few minutes longer than the round layers. Cool fully, brush the top with syrup and spread the buttercream over it. The cake will be lower and easier to transport, so cut it into squares rather than assembling layers.

Use a different citrus fruit: replace one lime with a lemon, keeping the total quantity of zest and juice close to the recipe amount. Lemon makes the cake sharper and less like the classic mojito flavour, but pairs naturally with mint. Avoid adding substantially more juice to the sponge, as extra liquid can change the crumb.

Add a coconut note: replace up to 30 g (¼ cup) of the flour with finely grated desiccated coconut. This gives a lightly chewy texture and a tropical suggestion without overwhelming the lime. For a dairy-free version, use a block-style plant butter and unsweetened plant milk; check that the butter substitute is suitable for creaming, since soft spreads can make the icing loose.

Make a stronger mint finish: increase the syrup mint to 15 g (about ¾ cup loosely packed), but do not add a large amount of chopped mint to the buttercream, where it can make the icing flecked and watery. For a more subtle flavour, leave the mint out of the sponge and rely on the infused syrup.

Storage and Reheating

Because this cake has buttercream, store it covered in the refrigerator and refrigerate it within 2 hours of serving. It keeps well for up to 4 days. Place it in an airtight cake container so it does not absorb other fridge smells. For the best texture, take slices out around 30–45 minutes before serving; this is not reheating, just allowing the buttercream and sponge to soften at room temperature.

You can freeze the undecorated sponge layers for up to 2 months. Wrap each completely cooled layer tightly in cling film, then place it in a freezer bag or airtight container. Defrost overnight in the refrigerator, still wrapped, then bring it to room temperature before brushing with syrup and icing. Slices of the finished cake can also be frozen in a sealed container, though the mint and lime garnish is best added fresh after thawing. Do not leave the cake at room temperature for more than 2 hours.

Frequently Asked Questions

Can I make mojito cake the day before?
Yes. Bake and assemble it the day before, cover it and refrigerate it. The syrup helps keep the sponge moist, and the lime and mint flavours will have time to settle. Add the fresh mint and lime garnish shortly before serving, then let the cake stand at room temperature for 30–45 minutes so it is not served fridge-cold.

Can I use plain flour instead of self-raising flour?
Yes. Replace the 250 g (2 cups) self-raising flour with 250 g (2 cups) plain flour and increase the baking powder to 3 teaspoons (12 g). Keep the salt amount the same. Check that your baking powder is in date, as old raising agent can leave the sponge flatter than expected.

Does the alcohol cook out of the cake?
No. The rum is stirred into the cooled syrup and icing, so it is not baked away. Leave it out if you want an alcohol-free cake; use the listed milk in the buttercream and simply omit the rum from the syrup. The fresh lime and mint still provide the defining flavour.

Why did my cake turn out dense?
Common causes are butter that was too cold to cream properly, overmixing after adding flour, or inaccurate flour measurements. Cream the butter and sugar until visibly lighter, fold the flour in gently, and check the layers with a skewer near the end of baking rather than leaving them in for much longer than needed.

Can I make the cake in one tin?
A single deep tin is not the best swap because the centre may take much longer to cook while the outside dries. Use the 23 cm (9-inch) square tin for a one-layer version, or bake the mixture in two batches if you only have one 20 cm (8-inch) round tin. Keep any waiting batter covered while the first layer bakes, and avoid leaving it out for an extended period.

What can I use if fresh mint is unavailable?
Fresh mint is preferable because it gives the syrup a clean, herbal aroma. If necessary, omit the mint rather than using a large amount of dried mint, which can taste dusty and will not give the same fresh finish. You can still make a bright lime cake with the syrup and zest, but it will be a lime cake rather than a close mojito-style version.

More recipes to cook

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

Spotted an error? Tell us and we will correct it (corrections policy).