This luscious cake's dark chocolate layers are accented by a rich yet not overly sweet frosting. The secret is to use buttermilk for moisture and high-quality cocoa for intense flavor.
And it's easier to prepare than most from-scratch cakes; you don't even have to take out the electric mixer. Raspberries and chocolate make an incredible combination, but if you don't have fresh, ripe berries, don't worry. The cake is also wonderfully delicious without them.
From Food to Live By: The Earthbound Farm Organic Cookbook by Myra Goodman
Make the Cake
Position a rack in the lower third of the oven and preheat to 350 degrees F. Butter the bottoms and sides of 2 round 9-inch cake pans. Dust the pans with some flour and tap out the excess. Set the pans aside.
Place the flour, 2/3 cup of cocoa powder, baking soda, salt and cornstarch in a medium-size bowl and sift it together into a large bowl.
Place the buttermilk, oil, eggs, granulated sugar and vanilla in a medium-size bowl and whisk to combine well.
Add the buttermilk mixture to the flour mixture and stir to blend. Divide the cake batter evenly between the two prepared cake pans. Bake the cakes until a toothpick inserted in the center comes out clean and the edges have pulled away from the sides, 20 to 30 minutes.
Cool the cake layers on wire racks for 10 minutes. Run a knife around the edge of each layer to loosen it from the pan. Invert the layers to unmold them, then replace on the racks to cool completely, about 45 minutes. At this point, the layers can be stored, tightly wrapped in plastic wrap, at room temperature for up to 24 hours.
Make the Frosting
Place the butter and bittersweet chocolate in a small saucepan and cook over low heat, stirring occasionally, until melted and smooth, 5 to 10 minutes.
Let the chocolate mixture cool for 5 minutes, then pour it into a large bowl. Sift in the 1/3 cup of cocoa powder and 1 cup of the confectioner's sugar. Add 1/4 cup of the sour cream and whisk to combine well. Sift in the remaining 1 cup of confectioner's sugar and stir until smooth. If the frosting is too stiff to spread easily, add 1 tablespoon of the remaining sour cream and stir to combine. If the frosting is still too stiff, gradually add just enough of the remaining sour cream to make it spreadable.
Melt the raspberry jam, if using, in a small saucepan over very low heat, about 3 minutes.
Assemble the Cake
If necessary, trim the cake layers so they're flat on top. Place one layer on a serving plate. Spread a third of the frosting on top of this layer. Spread all of the raspberry jam, if using, over the frosting. Arrange half of the fresh raspberries, if using, on the filling, splitting them in half with your fingers as you add them. Reserve the prettiest berries for the top of the cake.
Place the second cake layer on top of the first. Spread the remaining frosting on the top and sides of the cake. Arrange the remaining raspberries, if using, in concentric circles on top of the cake.
The cake can sit at room temperature for up to 6 hours or can be refrigerated, covered, for up to 3 days. For best flavor, serve the cake at room temperature.