Cinnamon Coffee Cake

Preheat the oven to 175°C (350°F). Grease a round cake pan or line it with parchment paper. Prepare the cinnamon sugar layer: In a small bowl, mix the granulated sugar and cinnamon well and set aside. Prepare the topping: In a medium bowl, combine the flour, granulated sugar, light brown sugar, cinnamon, and salt. Add the cold butter and cut it into the dry ingredients until the mixture resembles coarse crumbs. Cover and refrigerate while you make the cake batter. Prepare the cake batter: In a large bowl, whisk together the melted butter, sour cream, granulated sugar, light brown sugar, eggs, and vanilla extract until smooth. In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Add the dry mixture to the wet mixture and mix until just combined. Assemble: Pour half of the cake batter into the prepared cake pan and smooth the top. Sprinkle evenly with the cinnamon sugar layer. Pour the remaining batter over it and smooth again. Remove the topping from the refrigerator and sprinkle it evenly over the cake batter. Bake: Bake the cake for 40-45 minutes. Let the cake cool completely before carefully removing it from the pan. Slice and serve.