Preheat and prep: Heat the oven to 350°F (175°C). Grease an 8x8-inch baking pan or line it with parchment for easy lifting.

Make the cinnamon sugar: In a small bowl, mix 1/2 cup brown sugar with 2 teaspoons ground cinnamon. Set aside.

Combine dry ingredients: In a medium bowl, whisk 1 1/2 cups flour, 3/4 cup granulated sugar, 2 teaspoons baking powder, and 1/2 teaspoon salt.

Mix wet ingredients: In a separate bowl, whisk 3/4 cup milk, 1/2 cup melted unsalted butter (slightly cooled), 2 large eggs, and 1 1/2 teaspoons vanilla.

Make the batter: Pour the wet mixture into the dry ingredients. Stir gently until just combined. Don’t overmix—some small lumps are fine.

Layer and swirl: Pour half the batter into the pan. Sprinkle half the cinnamon sugar over it. Add the remaining batter, then the rest of the cinnamon sugar. Use a knife to gently swirl the top layer for a marbled look.

Bake: Bake for 28–34 minutes, or until the center is set and a toothpick comes out with a few moist crumbs. The top should be golden and fragrant.

Glaze it: Whisk 3/4 cup powdered sugar with 1–2 tablespoons milk or cream and 1/2 teaspoon vanilla until smooth. Drizzle over the warm dessert.

Rest and serve: Let it cool for 10–15 minutes so it sets slightly. Slice and serve warm.