Preheat the oven to 350°F. Line 18 cupcake pan with paper liners.
In a medium bowl, whisk together the flour, sugar, baking powder and salt; set aside.
In a large bowl use an electric mixer to blend the butter with the strawberry puree. Add the flour mixture and blend until light and fluffy (the batter will be very thick).
In another bowl, whisk together the egg whites, milk and dye. Add whites in three parts to the batter mixture, mixing only until incorporated after each addition.
Fill the cupcake liners about 3/4 full. Bake 18 to 22 minutes, or until toothpick inserted in center comes out clean.
Let the cupcakes cool completely before frosting.
Notes
*Use fresh strawberries if you wish, but put them in the freezer first to draw the moisture out of them, and then puree them as you would bagged frozen strawberries.