Preheat your oven to 175 degrees C (350 degrees F) and grease a 9x13-inch baking pan.
In a large bowl, combine 360 grams (3 cups) of flour, milk, white sugar, eggs, baking powder, 2 teaspoons of vanilla extract, salt, and melted butter. Mix until all the ingredients are well-combined.
In another large bowl, beat the softened butter, brown sugar, 2 tablespoons of flour, and cinnamon until smooth. Drop spoonfuls of this mixture over the batter in the baking pan. Use a knife to swirl the top layer into the bottom layer, creating a beautiful marble effect.
Bake the cake in the preheated oven for approximately 25 to 30 minutes or until a toothpick inserted into the center comes out nearly clean.
While the cake is still warm, prepare the glaze. In a large bowl, mix together the confectioners' sugar, milk, and 1 teaspoon of vanilla extract until smooth. Drizzle the glaze over the warm cake, allowing it to seep into the layers and add an extra touch of sweetness.