Preheat the oven to 350 degrees F. In a large bowl, create the cake mix according to package instructions. Set aside.
In a separate bowl, combine flour, brown sugar, sugar, cinnamon and vanilla extract. Add cold butter and mix together until you have a crumbly texture. Spray a 9 x 13 baking dish with nonstick spray.
Spread approximately ⅔ of the cake batter in the pan. Sprinkle half of the cinnamon sugar mixture on top. Layer with remaining cake batter and cinnamon sugar mix.
Then swirl the batter with a knife. Bake for approximately 25-30 minutes, or until golden brown and cooked through.
Use an inserted toothpick to test. If it comes back with moist crumbs attached it is done. Remove from the oven and let cool before slicing for at least 10 minutes.
Cake mix coffee cake muffins - Use same instructions but fill muffin pan with paper cups, 3/4 of the way full with batter with crumble gently pressed on top. Bake at 350 for 16-18 minutes or until they bounce back when gently touched in the center.
** If you want to make a simple glaze you can whisk together 1 cup powdered sugar + enough milk to make it as thick as you'd like and drizzle that on top of each piece.