Preheat your oven to 350°F (175°C). Gather all ingredients and equipment.

Cream together the butter, brown sugar, and granulated sugar until light and fluffy, then gradually add eggs, milk, and vanilla extract.

Sift in flour, baking powder, and cinnamon. Mix gently until combined.

Prepare the cinnamon swirl by mixing granulated sugar with cinnamon and melted butter.

Layer half of the batter, half of the cinnamon mixture, remaining batter, and swirl the remaining cinnamon mixture.

Bake for 25-30 minutes, checking for doneness with a toothpick.

Prepare the glaze by mixing powdered sugar and milk until smooth.

Drizzle the glaze over the cake once cooled slightly, then slice and serve.