Cinnamon Surprise Coffee Cake

Preheat the oven to 350 degrees F. Grease a 12-cup Bundt pan, a 9x13-inch baking pan, or two 9x5-inch loaf pans.

Prepare the cinnamon filling by mixing the cinnamon, butter, brown sugar, and flour in a bowl with a fork. The mixture should be crumbly. Set the filling aside.

In a bowl, combine the flour, baking powder, baking soda, and salt. Mix well.

In another mixing bowl, cream together the butter and sugar with an electric mixer on medium speed. With the mixer running, add the eggs one at a time, beating well after each addition. Add the vanilla and sour cream and mix until combined.

With the mixer running, slowly add the flour mixture to the egg mixture and mix until combined.

Place half of the cake batter in the Bundt pan (or place 1/4 of the batter in each loaf pan). Crumble the cinnamon mixture over the top. Pour the remaining cake batter over the cinnamon mixture and use a knife to gently swirl the batter and cinnamon slightly.

Place the pan(s) in the oven and bake at 350 degrees F for 50-60 minutes for the Bundt pan, or 35-40 minutes for the 9x13 pan or loaf pans, or until the cake tests done when a toothpick inserted in the middle comes out clean.

Remove the pan(s) from the oven and let the cake cool for 5 minutes in the pan then invert the cake onto a cooling rack. Let the cake cool thoroughly before slicing or storing in an airtight container. The cooled cake can also be sprinkled with powdered sugar or drizzled with a glaze, if desired.