Preheat oven to 350°F. Line muffin tin with cupcake liners.

Place strawberries in food processor, process until pureed. You should 1/3 cup of puree, set aside.

In medium bowl, whisk together flour, baking powder and salt, set aside. In small bowl, mix together milk, vanilla and strawberry puree, set aside.

With mixer, cream butter on medium high speed until light and fluffy. Gradually add sugar and continue to beat until well combined and fluffy. Reduce mixer speed to medium and slowly add egg and egg whites until just blended.

With 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 with spatula as necessary, until just blended.