Preheat oven to 350 degrees F.
With a hand or stand mixer, combine flour, salt, sugar, baking powder, milk, eggs and vanilla. Once combined, mix in melted butter.
Pour batter into a 9 x 13 inch baking pan sprayed with nonstick cooking spray.
In a large bowl, mix together softened butter, brown sugar, flour and cinnamon until combined.
Drop by spoonfuls over the batter and use a knife to swirl cinnamon topping into the cake for a marbling effect.
Bake for 25-30 minutes, or until an inserted toothpick comes out clean.
Whisk together all glaze ingredients until smooth and drizzle over warm cake.
Cut into slices and serve.