Preheat the oven to 350. Grease three 8-inch cake pans with non-stick spray.
Prepare your strawberry puree and set aside.
In the bowl of your stand mixer fitted with the paddle attachment, cream the butter and sugar for about 10 minutes, scraping the bowl occasionally, until fluffy and lightened in color.
Beat in the egg whites, one at a time, beating well after each. Scrape the bowl down again.
In a separate bowl, whisk together the strawberry puree, lemon juice, buttermilk and vanilla.
In another bowl, sift together the flour, baking powder, salt and freeze-dried strawberry powder.
With the mixer on low, add the dry ingredients in 3 additions, alternating with the wet ingredients, starting and ending with the flour. Mix just enough to combine, then use a spatula to finish bringing together the batter and stir in any dry bits. (If desired, add a few drops of red or pink food coloring with the wet ingredients.)
Divide the batter between the pans. Bake on the center oven rack for 25-30 minutes, until a cake tester in the center comes out clean and the tops of the cakes spring back when gently touched.
Set the pans on a wire rack, cover with a clean kitchen towel, and cool completely before frosting.