This cake is very barely adapted from Smitten Kitchen's sour cream chocolate cake, but it's so good, and pairs so well with all different frostings, like this simple and nutty tahini buttercream. —Joanna Sciarrino
Preheat the oven to 350°F. Butter the bottoms and sides of three 8-inch round cake pans. Line the bottom of each pan with a round of parchment or waxed paper and butter the paper.
Sift the flour, sugar, cocoa powder, baking soda, and salt into a large bowl and whisk to combine. In a separate bowl, whisk together the oil, sour cream, water, vinegar, vanilla, and eggs.
Gradually add the dry ingredients to the wet ingredients until the batter is completely combined. Divide among the 3 prepared cake pans.
Bake for 30 to 35 minutes, or until a toothpick comes out almost clean. Let cool in the pans for about 20 minutes. Invert onto wire racks, carefully peel off the paper liners, and let cool completely and then chill overnight.
Beat the butter and tahini together until smooth. Gradually add in the powdered sugar, then the vanilla and the salt. Continue to beat until completely smooth and lightened in color, about 2-3 minutes on medium speed.
Frost the cake: Place one cake layer, flat side up, on a cake stand or large serving plate. Spread with an even layer of the buttercream. Repeat with the next layer. Place the last layer on top and frost the top and sides of the cake with a thin layer of frosting to bind any crumbs together. Chill the cake for 30 minutes or until the crumb coat is set. When the cake is chilled, frost with a thick layer of buttercream. Then use the remaining buttercream to create big swooshes and swoops across the entire exterior. Sprinkle with sesame seeds, slice, and serve.