Preheat the oven to a temperature of 350°F (175°C). Prepare a 9x13-inch baking dish by applying a nonstick cooking spray with flour.

In a large mixing bowl, or using a stand mixer, combine the all-purpose flour, white granulated sugar, baking powder, large eggs, vanilla extract, and milk.

While mixing, gradually incorporate the melted salted butter. Mix until the ingredients are well-combined, ensuring not to overmix to maintain the texture of the final product.

Transfer and evenly distribute the batter into the previously prepared baking dish.

In a separate bowl, amalgamate the room temperature salted butter, packed light brown sugar, all-purpose flour, and ground cinnamon until well combined.

Distribute spoonfuls of the cinnamon filling onto the surface of the cake batter.

Utilize a butter knife to create a marbled effect by swirling it through the cake batter and cinnamon filling.

Place the cake in the preheated oven and bake for approximately 35-40 minutes, or until a knife or skewer inserted into the cake's center emerges clean.

In a bowl, whisk together the powdered sugar, milk, and vanilla extract to achieve a smooth consistency. Adjust the texture by modifying the amounts of powdered sugar or milk if required.

Pour the glaze uniformly over the warm cake.