3 6 oz packs blackberries
1/3 cup milk, at room temperature
6 large egg whites, room temperature
2 tsp lemon juice
2 1/4 cup cake flour, sifted
1 3/4 cup sugar
4 tsp baking powder
1 tsp salt
12 Tbsp unsalted butter (1 1/2 sticks), softened
For the frosting:
2 sticks butter unsalted butter, softened
1/2 tsp vanilla
1/4 tsp almond extract
5 cups confectioner’s sugar
1 Tbsp meringue powder
pinch of salt
1/4 cup blackberry puree