Jewel sheet cake is a tender vanilla cake baked in a single rectangular pan and finished with frosting and jewel-bright candies or sprinkles. It is easy to portion for a gathering, and the colorful topping makes a simple, adaptable celebration cake without needing special decorating tools.
Ingredients
- 2 ½ cups (300 g) all-purpose flour, spooned into the measuring cup and leveled
- 1 ½ cups (300 g) granulated sugar
- 2 teaspoons (8 g) baking powder
- ½ teaspoon (3 g) fine salt
- ½ cup (113 g) unsalted butter, softened, plus extra for the pan
- 2 large eggs, at room temperature
- 1 cup (240 ml) whole milk, at room temperature
- 2 teaspoons (10 ml) vanilla extract
- 1 tablespoon (15 ml) neutral oil, such as canola or sunflower oil
- 2 cups (240 g) powdered sugar
- 3 tablespoons (45 ml) softened unsalted butter for the frosting
- 2 tablespoons (30 ml) milk or cream, plus more as needed
- ½ teaspoon (2.5 ml) vanilla extract for the frosting
- ⅛ teaspoon fine salt for the frosting
- ½ cup (90 g) colorful candy-coated chocolate pieces, chopped if large, or jewel-colored sprinkles
Instructions
- Heat the oven to 350°F (175°C). Grease a 9-by-13-inch (23-by-33-cm) metal baking pan and line the bottom with parchment, leaving a little overhang to lift the cooled cake out. If using a glass pan, check it early because it may bake differently.
- In a medium bowl, whisk together the flour, baking powder, and salt. In a larger bowl, beat the softened ½ cup (113 g) butter with the sugar for about 2 minutes, until creamy and a little lighter in color. A hand mixer or stand mixer works; a sturdy whisk and some elbow grease do too.
- Beat in the eggs one at a time, scraping down the sides of the bowl. Mix in the vanilla and oil. The batter may look slightly separated; it will come together when the dry ingredients and milk are added.
- Add about one-third of the flour mixture and mix on low just until combined. Mix in half the milk, then repeat with another third of the flour, the remaining milk, and the remaining flour. Stop as soon as no dry streaks remain. Scrape the bowl once; overmixing can make the cake tough.
- Spread the batter evenly in the prepared pan, nudging it into the corners. Bake for 26–32 minutes, rotating the pan once if your oven browns unevenly. The top should spring back gently when touched, and a toothpick inserted near the center should come out clean or with a few moist crumbs. If using a thermometer, the center should reach about 200°F (93°C), a doneness guide for cake rather than a food-safety minimum.
- Set the pan on a rack and let the cake cool completely, about 45 minutes. Frosting a warm cake will cause the buttercream to melt and slide. To make the frosting, beat the 3 tablespoons (45 ml) butter until smooth. Add powdered sugar, 2 tablespoons (30 ml) milk or cream, vanilla, and salt. Beat until fluffy, adding more milk a teaspoon at a time if it is too stiff, or a little more powdered sugar if it is loose.
- Spread the frosting over the cooled cake. Scatter the candy or sprinkles over the top while the frosting is still soft, pressing gently so they adhere. Lift the cake out with the parchment, if desired, and cut into 16 squares with a clean knife.
Tips
- Measure flour by spooning it into the cup and leveling the top, or weigh it. Scooping directly with the cup can pack in too much flour and make the crumb dry.
- For a softer, more even crumb, bring the eggs and milk to room temperature. If you forget, place the eggs in warm water for about 5 minutes and briefly warm the milk; do not use hot liquid.
- Use sprinkles rather than chopped candy if the cake will sit out for a while. Some candy coatings can bleed color onto frosting, especially in a humid room. Add the topping shortly before serving for the neatest appearance.
- For an easy dairy-free version, use a plant-based butter stick and unsweetened oat or soy milk. The flavor and frosting texture may vary; choose a butter-style block rather than a soft tub spread for better structure.
Serving Suggestions
Serve the cake at room temperature, when the frosting is soft and the vanilla flavor is most noticeable. It pairs well with coffee, tea, or a glass of milk. For a party, cut it into smaller squares and arrange them on a platter; for a plated dessert, add fresh berries alongside rather than piling moist fruit onto the frosting. A scoop of vanilla ice cream is also a fitting choice for a birthday or other celebration.
Variations
For a citrus version, add 1 tablespoon (6 g) finely grated lemon or orange zest to the sugar before beating in the butter, and use a little citrus juice in place of some frosting milk. For a chocolate cake, replace ½ cup (60 g) of the flour with ½ cup (42 g) unsweetened cocoa powder and add 2 tablespoons (30 ml) extra milk if the batter seems unusually thick.
You can tint the frosting with a small amount of gel food coloring, or divide it into bowls for several colors. For a less sweet finish, use a thinner frosting layer and choose a modest amount of colorful sprinkles instead of candy-coated chocolates. If you want a nutty topping, add ¼ cup (30 g) finely chopped toasted pistachios with the candies; keep the finished cake away from anyone with a nut allergy.
Storage and Reheating
Because this cake has a simple buttercream rather than a cream-cheese or whipped-cream topping, it can be kept covered at cool room temperature for up to 2 days. Refrigerate it within 2 hours if the room is warm or if it will not be eaten within that time; refrigerated, it keeps well for 3–4 days. Store it in an airtight container so the cake does not dry out or absorb refrigerator odors. Let chilled slices sit at room temperature for 20–30 minutes before serving; reheating is usually unnecessary. For longer storage, freeze unfrosted cake or individual frosted portions, tightly wrapped, for up to 2 months. Thaw in the refrigerator, then bring to room temperature before serving.
Frequently Asked Questions
Can I bake this cake in a different pan?
A 9-by-13-inch (23-by-33-cm) pan gives the stated baking time and thickness. A deeper or smaller pan needs longer and may leave the center underbaked before the edges are done. For cupcakes, divide the batter among lined wells and begin checking around 18 minutes; the yield and timing will depend on the pan size.
How do I know when the cake is done?
Look for a lightly golden top that springs back when gently pressed and a toothpick with no wet batter. Start checking at 26 minutes because ovens and pans vary. A toothpick with a few soft crumbs is fine; a completely dry one can mean the cake has baked too long.
Can I make the cake ahead?
Yes. Bake it a day ahead, cool completely, and keep it covered. You can frost it the same day or the next. If you freeze the unfrosted cake, wrap it well once cool and thaw it while still wrapped so condensation forms on the wrapping rather than the cake.
Why did my cake turn out dense?
Common causes include too much flour, old baking powder, cold ingredients, or mixing the batter too long after adding flour. Check that your baking powder is fresh, measure carefully, and mix only until the last flour streaks disappear.
Can I use a different topping?
Yes. Use colored sprinkles, chopped candy, or a mix of both. For a cleaner cut, choose small sprinkles or chop larger candies into bite-size pieces. Add the topping after frosting, while the surface is still soft enough to hold it.
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