Preheat the oven to 350 and grease a 9x9 or 9x11 inch baking dish with cooking spray.
First, in a bowl whisk together flour, brown sugar, sugar, salt, and cinnamon. Cut in chilled butter until crumbly. Set aside.
Next, in a large bowl combine cake mix, water, egg, sour cream, melted butter, and vanilla and mix until combined.
Spread half the cake batter in the bottom of the greased baking dish.
Sprinkle half of the crumble mixture.
Then, top with dollops of remaining cake batter and spread with a greased rubber spatula and gently spread the remaining batter over the crumble
Top with remaining crumble.
Bake for 30-35 minutes until an inserted toothpick comes out clean.
While the cake is baking, prepare the glaze and drizzle over the cake after it’s cooled for about 10 minutes.