Preheat oven to 350 F.
Grease, flour and line two 9-inch cake pans.
Sift together the flour, baking powder, salt, pudding, and strawberry Jell-O. Set aside.
Cream butter in a large bowl until light and fluffy for 2 minutes on medium speed.
Add sugar and continue to mix until light and fluffy.
Add egg whites one at a time. Mix well.
Add vanilla extract.
Reduce the mixer speed to low and add the dry ingredients alternately with the sour cream and milk beginning and ending with the flour. Be sure the mixture is completely blended after each addition.
Finally add 1 cup of strawberry puree.
Pour the batter into the prepared pans. Bake in the preheated oven for about 35-40 minutes or until an inserted toothpick comes out clean.
Let cakes cool completely on a rack before frosting.