Starbucks Coffee Cake copycat

Box Yellow Cake Mix (plus ingredients on back of box)

2 Sticks cold salted butter

   2 1/4 Cups flour

   1 1/2 Tablespoons cinnamon

   1 3/4 Cups brown sugar

    1 1/2 Tablespoons vanilla

    Powdered sugar (for dusting)

Prepare cake mix in large bowl according to directions on box. Spray 9 X 13 pan with non-stick spray. Pour batter into pan. Bake at 350 for 15-20 minutes or until center is just barely set. 

While cakes are baking, prepare crumb topping. In large bowl with electric mixer combine, butter, flour, cinnamon, brown sugar and vanilla until all crumbly. Immediately after cake is removed from oven, break crumb topping into marble size pieces with fingers, sprinkling 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, using a sieve. Cut into squares and serve.