Soft, delicious cupcakes made with key lime zest for a beautiful citrus flavor and topped with blueberry cream cheese frosting that's made with fresh blueberry syrup.
Add blueberries into a small sauce pot, heating over medium heat.
Add lemon juice and sugar. Stir well.
Cover (leaving a crack for the steam to escape) and cook for about 15 minutes, stirring often. (Watch it closely, it may over-run.)
Strain off some juice (about 3 Tbsp) for topping the cupcakes and puree the rest in a blender.
Cupcakes:
Preheat the oven to 350 and line a muffin pan with cupcake liners.
Sift flour, baking soda, salt and baking powder together and set aside.
Make sure your other ingredients are ready.
In a bowl of an electric mixer (use paddle attachment), beat egg whites for a few seconds and slowly start pouring in sugar. Beat for 3-4 minutes, until white and fluffy.
Start pouring in oil, slowly, as the eggs are still beating on medium-high.
Add vanilla and lower the speed to low.
Alternating, add flour mixture and buttermilk in two parts. Mix until just combined.
Add key lime zest. Make sure to scrape sides and bottom of the bowl and mix until all incorporated.
Divide batter among the cupcake cups, filling them about 2/3 of the day.
Bake for 18-20 minutes.
Cool completely before frosting!
Frosting:
Beat butter and cream cheese together, on medium-high speed, until smooth, 1-2 minutes.
Lower the speed to low and beat in powder sugar and blueberry sauce.
Turn up the speed back to medium-high and beat for about 3-4 minutes, until the frosting is light, smooth and fluffy.
Frost the cupcakes and drizzle blueberry sauce that you've set aside on each cupcake.