01 -
Preheat oven to 350°F and grease a 9×13-inch baking dish with nonstick cooking spray containing flour.
02 -
In a large bowl, combine flour, sugar, and baking powder. Add eggs, vanilla extract, and milk. Begin mixing and slowly pour in melted butter. Stir just until combined to avoid overmixing.
03 -
Evenly pour and smooth the batter into the prepared baking dish, creating a level surface.
04 -
In a separate bowl, blend softened butter, brown sugar, flour, and cinnamon until a thick spread forms.
05 -
Drop spoonfuls of the cinnamon mixture over the batter. Use a butter knife to gently swirl the filling, forming a marbled pattern without fully mixing.
06 -
Bake for 35 to 40 minutes, until a knife inserted in the center comes out clean. Adjust baking time based on oven variance.
07 -
While baking, whisk powdered sugar, milk, and vanilla until smooth. Adjust consistency as desired.
08 -
Allow cake to cool slightly before pouring glaze evenly over the top. Serve warm or at room temperature.