Step 1

Preheat the oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking pan.

Step 2

Mix flour, sugar, milk, eggs, baking powder, vanilla, and salt for cake together in a large bowl until completely combined. Slowly pour in butter and mix to incorporate; pour into the prepared baking pan.

Step 3

Whisk brown sugar, flour, and cinnamon for topping together in a bowl. Cut in butter with 2 knives or a pastry blender until well combined. Drop evenly over the batter, then swirl with a knife.

Step 4

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 30 to 40 minutes.

Step 5

Mix powdered sugar, milk, and vanilla for glaze together in a small bowl. Drizzle over the warm cake.