Preheat your oven to 350°F and lightly coat a 9×13-inch baking dish with nonstick cooking spray. In a large bowl, mix together 3 cups of flour, 1 cup of sugar, 4 teaspoons of baking powder, 2 eggs, 2 teaspoons of vanilla extract, and 1 ½ cups of milk using a hand mixer until well combined.

With the mixer set to low speed, gradually add in ½ cup of melted butter and continue mixing until combined. Spread the batter evenly into the prepared baking dish.

In a medium or small bowl, combine ¾ cup of softened butter, 1 cup of brown sugar, 2 tablespoons of flour, and 1 tablespoon of cinnamon. Stir until thoroughly mixed.

Drop spoonfuls of the cinnamon mixture into the batter and use a butter knife to create swirls throughout the cake by dragging the knife through both the cake batter and the cinnamon mixture.

Bake for 35-40 minutes, or until a knife inserted into the center comes out clean.

For the glaze, whisk together 2 cups of powdered sugar, 5 tablespoons of milk, and 1 teaspoon of vanilla extract in a small bowl. If the glaze isn’t thick enough, refer to the tips and tricks.

Pour the glaze over the warm cake, slice, and serve. Enjoy!