Preheat the oven to 350 degrees.
Put 12 paper liners into a cupcake tin or better yet, use silicone baking cups
Whisk the flour, baking powder, baking soda, and salt together. Set aside.
In a large mixing bowl, whip the butter and granulated sugar until fluffy.
Mix in the egg and then the egg whites.
In a separate bowl, whisk together the buttermilk, strawberry puree, and vanilla extract.
Alternately add the flour and buttermilk mixtures to the large mixing bowl with the butter, sugar, and eggs until just combined.
Fold 1 cup of the diced strawberries into the batter.
Scoop the batter into the cupcake pan, filling each one two-thirds full.
Bake 20 to 24 minutes.