01 -
Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking pan.
02 -
Combine flour, milk, white sugar, eggs, baking powder, vanilla extract, and salt in a large bowl. Mix thoroughly until smooth. Stir in melted butter and pour the batter into the prepared pan.
03 -
In a separate bowl, beat softened butter, brown sugar, flour, and cinnamon until smooth. Drop spoonfuls of the mixture over the batter in the baking pan.
04 -
Using a knife, swirl the cinnamon filling into the batter to create a marble effect.
05 -
Bake in the preheated oven for 25 to 30 minutes, or until a toothpick inserted into the center comes out nearly clean.
06 -
Whisk together confectioners' sugar, milk, and vanilla extract in a bowl until the glaze is smooth.
07 -
Drizzle the glaze over the warm cake before serving.