2/3 cup whole fresh or frozen strawberries, thawed
1 1/2 cups all-purpose flour, sifted
1 teaspoon baking powder
1/4 teaspoon coarse salt
1/4 cup whole milk, room temperature
1 teaspoon pure vanilla extract
1/2 cup (1 stick) unsalted butter, room temperature
1 cup sugar
1 large egg, room temperature
2 large egg whites, room temperature
Step One: Preheat oven to 350 degrees. Line a 12-cup muffin tin with cupcake liners.
Step Two: Place strawberries in a small food processor; process until pureed. You should have about 1/3 cup of puree, add a few more strawberries if necessary or save any extra puree for frosting; in a small bowl, mix together milk, vanilla, and strawberry puree; set aside .
Step Three: In a medium bowl, whisk together flour, baking powder, and salt; set aside. Cream butter on medium-high speed, until light and fluffy and gradually add sugar and continue to beat until well combined and fluffy. Reduce the mixer speed to medium and slowly add egg and egg whites until just blended.
Step Four: With the mixer on low, slowly add half the flour mixture; mix until just blended. Add the milk mixture; mix until just blended. Slowly add remaining flour mixture, scraping down sides of the bowl with a spatula, as necessary, until just blended.
Fill tins 2/3 of the way up and transfer muffin tin to oven and bake until tops are just dry to the touch, 22 to 25 minutes. Let cool completely before frosting.