For the cinnamon sugar swirl: 1/2 cup brown sugar, 2 tsp ground cinnamon, 2 tbsp all-purpose flour, 2 tbsp melted butter
Instructions
Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan.
Cream together the butter and sugars until light and fluffy.
Add eggs one at a time, mixing well after each addition. Stir in vanilla.
In a separate bowl, whisk together flour, baking powder, baking soda, and salt.
Alternate adding the flour mixture and buttermilk to the butter mixture, starting and ending with the flour.
Pour half the batter into the prepared pan, sprinkle with half the cinnamon sugar topping, then add remaining batter and top with the rest of the topping.
Visualize the swirls gently with a knife.
Bake for 35–40 minutes, or until a toothpick inserted comes out clean.
Let cool slightly before slicing and serving.
Notes
For a gluten-free version, substitute with a gluten-free all-purpose blend. You can also add nuts or fruits for extra texture.