Key Lime Cupcakes with Key Lime Ermine Frosting
These Key Lime Cupcakes are soft, buttery, and packed with bright citrus flavor in every bite. Fresh key lime juice and zest give the cupcakes a vibrant, tangy taste, while the key lime ermine frosting adds a silky, lightly sweet finish that melts right into the cupcake.
Servings: 12 cupcakes
Calories: 406kcal
Ingredients
Key Lime Cupcakes
- 1 ½ cups (187.5 g) all-purpose flour
- 1 ½ teaspoons baking powder
- ½ teaspoon kosher salt
- ½ cup (1 stick / 113 g) unsalted butter, softened
- ¾ cup (150 g) granulated sugar
- 2 large eggs, room temperature
- ½ cup whole milk, room temperature
- 1 teaspoon vanilla extract
- 1* tablespoon key lime zest, from 1 to 2 key limes
- ⅓ cup key lime juice, from about 8 to 12 key limes (or bottled key lime juice)
Key Lime Ermine Frosting
- ¾ cup fresh key lime juice, from about 18 to 24 key limes (or bottled key lime juice)
- 5 tablespoons all-purpose flour
- 1 cup (2 sticks / 227 g) unsalted butter, room temperature
- 1 cup (200 g) granulated sugar
- 2 to 3 tablespoons key lime zest, from 3 to 4 key limes
- ½ teaspoon vanilla extract
- Pinch kosher salt
Instructions
Key Lime Cupcakes
- Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners.
- In a medium bowl, whisk together the flour, baking powder, and salt.
- In the bowl of a stand mixer with the paddle attachment (or using a handheld mixer), beat the butter and sugar until light and fluffy, about 2 to 3 minutes.
- Add the eggs one at a time, beating well after each addition.
- Mix in the vanilla extract, key lime zest, and key lime juice.
- With the mixer on low speed, add half of the flour mixture. Pour in the milk and mix until combined. Add the remaining flour mixture and mix just until incorporated. Do not overmix.
- Divide the batter evenly among the cupcake liners, filling each a little over halfway full.
- Bake for 20 to 24 minutes, or until the tops spring back lightly when touched and a toothpick inserted into the center comes out clean.
- Let the cupcakes cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
Key Lime Ermine Frosting
- In a medium saucepan over medium heat, whisk together the key lime juice and flour until smooth.
- Cook, whisking constantly, until the mixture thickens to a pudding-like consistency and begins to bubble, about 2 to 4 minutes. Continue cooking for 1 additional minute while whisking.
- Remove from heat and transfer the mixture to a shallow bowl or plate. Press plastic wrap directly onto the surface and let cool completely to room temperature.
- In the bowl of a stand mixer with the paddle attachment (or using a handheld mixer), cream the butter and sugar together on medium-high speed until very light and fluffy, about 4 to 5 minutes.
- Add the cooled lime mixture, lime zest, vanilla extract, and salt. Beat on medium speed until combined, then increase to high speed and whip until smooth, light, and fluffy, about 3 to 5 minutes more.
- If the frosting feels too soft for piping, refrigerate for 15 to 30 minutes before frosting the cupcakes.
- Pipe or spread frosting onto completely cooled cupcakes and garnish with additional lime zest if desired.
Notes
*Can use up to four tablespoons, depending on how much zest you'd prefer. When we tested with four, it was very tart, but good if you love tart.
Nutrition
Serving: 1cupcake with frosting | Calories: 406kcal