- 3/4 cup packed dark brown sugar
- 1/4 cup heavy cream
- Pinch of salt
- 1 cup chopped toasted nuts (pecan, walnuts, almonds, hazelnuts, or any combination)
- 1/2 cup packed dark brown sugar
- 1/3 cup all-purpose flour
- 4 tablespoons butter, cut into pieces
- 1 tablespoon cinnamon
- 1/4 teaspoon salt
- 1 1/2 cups all purpose flour
- 1/2 teaspoon baking powder
- 1/2 teaspoon baking soda
- 1/2 teaspoon salt
- 1/2 cup buttermilk
- 1/4 cup sour cream ( regular or light)
- 2 eggs
- 1/2 teaspoon vanilla bean paste, or 1 teaspoon vanilla extract
- 1/2 cup (1 stick) butter, softened
- 3/4 cup granulated sugar
- Preheat oven to 350˚F. Spray a 9×2-inch round cake pan with nonstick spray. (Make sure the pan is at least 2 inches deep.)
- Measure the 1/4 cup cream into a liquid measuring cup. Add the brown sugar and salt, stir to combine. Pour caramel into the prepared cake pan, spreading to cover the bottom of the pan. Sprinkle the nuts over the caramel.
- Process the brown sugar, flour, butter, cinnamon and salt for the streusel in a food processor. Pulse mixture until sandy but without clumps. Set aside.
- In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
- In a medium bowl, whisk together the buttermilk, sour cream, eggs, and vanilla. Set aside.
- In the bowl of an electric mixer, cream together the butter and granulated sugar just until combined. Alternately add the flour mixture and the buttermilk mixture to the creamed mixture, starting and ending with the flour mixture. Blend only enough to incorporate the dry ingredients into the batter.
- Drop half the batter by spoonfuls over top the caramel in the cake pan. Spread batter with an offset spatula or a spoon to cover the caramel. Sprinkle with half of the streusel. Spoon remaining batter over streusel, spreading to cover. Top with remaining streusel.
- Bake coffee cake until a toothpick inserted in the center comes out clean, 50-60 minutes. Cool cake for 5 minutes on a rack, then run a knife around the sides to loosen cake. Invert cake onto a serving plate while hot. Let cool slightly before serving.