Based on a version that appeared in Epicurious. It's a good recipe if you use the right type and the right amount of flour. If you do not have a scale, sift the cake flour and then measure or just use 1 ¾ cups. If you do have a scale, weigh out 210 grams. Also, I feel like the baking powder amount in the original recipe is a little high compared to others. Next time I might try it with just ½ teaspoon.
2 ¼cupssifted cake flour (210 grams, which would be about 1 ¾ cup unsifted(210 grams)
2tablespoonsnatural unsweetened cocoa powder
1teaspoonbaking soda
1teaspoonbaking powder (I think ½ would work but haven't tested)
½teaspoonsalt
1cupbuttermilk at room temperature
2tablespoonsred food coloring1 oz bottle
1teaspoonvanilla extract
1teaspoonvinegar
½cupunsalted butter, softened(114 grams)
1 ½cupsgranulated sugar(300 grams)
2largeeggs
Frosting
16ouncecream cheeseroom temperature
½cupunsalted butter, room temperature
1tablespoonvanilla extract
2 ½cupspowdered sugar
Berries
6cups berries, use a mix of rasberries and blueberries. I don't see why you couldn't throw in blackberries.
Instructions
Preheat oven to 350 degrees. Spray two 9-inch round pans with flour added cooking spray or rub with shortening and dust with flour. The original recipe calls for 9 inch pans. I think 8 inch pans would work too.
Whisk together sifted cake flour, cocoa, baking soda, baking powder and salt; set aside.
In a measuring cup, mix together the buttermilk, red food coloring, vanilla and vinegar.
In a mixing bowl, beat the butter and sugar until creamy, scraping the bowl often. Beat in the eggs one by one.
Add the flour mixture and buttermilk mixture alternately.
Beat with an electric mixer until smooth, stopping to scrape the bowl.
Divide batter between pans and bake cakes on center rack for 25-28 minutes or until a wooden skewer inserted in center comes out clean. If using 8 inch pans, the cakes will probably take a little longer.
Cool in pans on racks 10 minutes. Turn cakes out onto racks and let cool completely.
Frosting
Beat cream cheese and butter in large bowl until smooth. Beat in vanilla. Add powdered sugar and beat until smooth.
To frost the cake, frost a layer and embed a mixture of fresh raspberries and blueberries in the frosting. Stack on the second layer. Frost the cake and arrange the rest of the berries decoratively.