For the cake, preheat oven to 350 degrees.
Grease two 8-inch cake pans, lining the bottom with parchment paper.
In mixer, blend 3 cup flour, sugar, salt, baking powder, milk, eggs, vanilla and 1/4 cup melted butter.
Divide batter evenly between cake pans.
In another mixing bowl, beat 1 cup butter with brown sugar, 2 tablespoons flour, and cinnamon. Continue to beat until fully blended and fluffy (about 3 minutes).
Using two tablespoons, drop butter mixture onto cake batter. Use a knife to swirl.
Bake cakes for about 25-30 minutes.
Remove from oven and cool in pans 10 minutes. Flip cakes out onto serving plates.
For icing, whisk the powdered sugar with 1/4 cup milk and 1 teaspoon vanilla extract.
Drizzle over warm cakes.