Mix in the buttermilk and lemon juice on low until the batter is smooth and well combined.
120 grams buttermilk, 120 grams lemon juice
Distribute the batter between the 3 prepared pans.
Bake for 25-30 minutes until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 20 minutes, then flip onto a wire cooling rack and let cool completely.
Mascarpone Frosting
In a mixing bowl, beat the mascarpone with softened butter until creamy.
Level the tops of the cakes with a serrated knife if needed.
Place one layer on a cake stand or cardboard round. Evenly spread a thin layer of frosting across the top.
Pipe a ring of frosting around the edge.
Fill the center with ⅓ cup of berries spreading them to the buttercream boarder.
Continue layering the same way with the second layer.
Place the last layer upside-down so the top is flat.
Cover the sides and top of the cake with a thin layer of buttercream, or "crumb coat".
Once the crumb coat is applied, chill the cake in the freezer for 20 minutes.
Apply a final thick layer of frosting to the sides and top of the cake. Garnish with fresh berries and enjoy.
Video
Notes
Measure your flour correctly by weighing it in grams with a kitchen scale. If you don't have a scale, fluff up the flour first and then spoon it into your measuring cup.Check on the cake a few minutes before the suggested baking time as oven temperatures can vary. It's done when a toothpick inserted in the center comes out clean.Chill the cake before decorating to make it easier to handle and prevent frosting from melting.Storage: Store for 4-5 days in an airtight container in the refrigerator. I recommend storing it without berries on top.Freezing: Freeze with or without frosting for up to 3 months in an airtight, freezer safe container. Remove the berries on top before freezing.