Create the Cinnamon Swirl: Combine brown sugar and cinnamon in a small bowl, then sprinkle it over the batter. Microwave: Heat on high for 90 seconds or until a toothpick comes out clean.

Cake Batter: 2 cups all-purpose flour 1½ cups sugar 1 teaspoon baking powder ½ teaspoon baking soda ½ teaspoon salt 1 cup buttermilk 2 large eggs 1 teaspoon vanilla extract ½ cup unsalted ...