4.

Move the oven rack to the center position and preheat the oven to 375°F. Add remaining 4 tablespoons butter, brown sugar, and cinnamon, to the bowl of a food processor. Pulse until thoroughly combined. Using your index finger, poke deep holes evenly across the surface of the cake. Swirl your finger to widen the hole to create wells for the topping. Fill each hole with cinnamon and sugar topping. Bake until golden on top and done in the middle, about 30 to 35 minutes. Serve warm.