Directions: Preheat oven to 350 degrees. Spray a 9x13 glass baking pan with cooking spray. Set aside.
In an electric or stand mixer add the flour, salt, sugar, baking powder, milk, eggs, and vanilla. Once combined well , slowly stir in the melted butter. Pour into the prepared 9x13 baking pan.
For topping, In a large bowl mix the 2 sticks of butter, brown sugar, flour and cinnamon together until well combined and creamy. Drop evenly over the batter by the tablespoonfuls and use a knife to marble/swirl through the cake.
Bake at 350 for 28-32 minutes or when a toothpick inserted near the center comes out nearly clean.
FOR GLAZE: In a medium bowl, mix the powdered sugar, milk and vanilla together with a whisk. Drizzle evenly over the warm cake. Serve warm or at room temperature.
Tips: The topping will be thick and I did not get mine swirled evenly throughout the cake. But it was still good!
Mine took a lot longer than 28-32 minutes to cook. It probably took closer to 50 min. I kept checking with a toothpick (I believe it was my oven though, Need to check the temp!)