1tablespoonfreshly grated key lime zest, about 4 key limes
1 1/4teaspoonspure vanilla extract
2egg whites, room temperature
1 1/2cupscake flour, sifted
3/4cupssugar
2teaspoonsbaking powder
1/4teaspoonsalt
3tablespoonsunsalted butter, room temperature
3tablespoonsvegetable shortening
Key Lime Buttercream
1cupunsalted butter, room temperature
3 1/2cupspowdered sugar, sifted
4tablespoonsfresh key lime juice, about 15 to 18 key limes*
1/2teaspoonpure vanilla extract
1/8teaspoonsalt
Instructions
Key Lime Cupcakes
Preheat oven to 350°F and line a standard muffin pan with cupcake liners.
In a microwave-safe bowl, stir together the milk and zest. Microwave until just warmed, about 30 seconds. Allow to cool to room temperature.
In a small bowl, whisk together 1/8 cup of the milk mixture with the vanilla and egg whites. Set aside.
In the bowl of a stand mixer fitted with the paddle attachement, mix together the flour, sugar, baking powder and salt on low speed until combined.
Add the butter and shortening and mix on medium until combined, resembling a seedy consistency (see photo above). Slowly add the remaining 3/8 cup of milk and continue to beat until moistened.
Reduce the speed to low and add the egg mixture in three additions, scraping down the sides of the bowl as necessary between each addition.
Fill each well of the prepared muffin pan 2/3 full. Bake for 16 to 18 minutes, until a toothpick inserted into the center of the center cupcake comes out clean.
Allow the cupcakes to cool in the pan on a cooling rack for 5 minutes. Transfer the cupcakes to a cooling rack to cool completely before frosting.
Key Lime Buttercream
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed until pale and creamy.
Reduce the speed to low and add the powdered sugar, 1/2 cup at a time. Scrape down the side and bottom of the bowl with a rubber spatula.
Add the key lime juice to the mixture, followed by the vanilla and salt. Continue mixing on low until combined. Increase the speed to medium for 10 to 15 seconds, until whipped and fluffy.
Frost cooled cupcakes using an offset spatula or a piping bag and your favorite tip**. Garnish with key lime zest.
Notes
*Pro-tip: To make juicing the key limes easier, microwave them for 10 to 20 seconds, until slightly warmed. Then, roll each lime on the work surface using the palm of your hand to soften the flesh before cutting and juicing.**The cupcakes above were piped with Ateco tip #887.Substituting limes for key limes: Use the equivalent amount of zest or juice, NOT the equivalent amount of limes.