Preheat oven to 350F. Prepare cake mix in large
bowl according to directions on box. Spray 9x13
pan with non-stick spray. Pour batter into pan.
Bake at 350F for 15-20 minutes or until center is
just barely set.
While cake is baking, prepare crumb topping. In
large bowl of electric mixer combine butter,
flour, cinnamon, sugar, and vanilla until all
Immediately after cake is removed from oven,
sprinkle mixture over top. Put back in oven and
bake an additional 10-15 minutes (topping will
begin to look a little less wet/raw). Let cool
fully then dust with powdered sugar.
Cut and serve.