A delightfully simple, moist, make-ahead coffee cake bursting with flavor and loads of crumb! Inspired by Starbucks Coffee Cake. Plus Gluten free instructions.
Preheat oven to 350° and spray two 8x8 pans with non-stick spray or one 9x13 pan.
Prepare cake mix in a large mixing bowl according to box instructions. It's helpful if the bowl has measurements if you plan on splitting the batter. If you are using butter in place of oil, make sure you have cooled the butter slightly to avoid "cooking" your eggs.
Mix 2 minutes on medium-high, scraping down sides of bowl once. Pour batter into prepared pan(s). Bake at 350 for 12-18 minutes, until center is wiggly, barely set, not soupy.
Crumb Topping
In a large bowl of a mixer with a paddle attachment, combine butter, flour, brown sugar, vanilla and salt and mix until butter incorporated and mixture is uniform without large chunks of butter.
Once cakes are finished with initial baking, remove and immediately crumble the topping over the hot cake(s), spreading evenly.
Return to the oven and continue baking an additional 10-15 minutes. If you will be freezing or serving later, pull out on the earlier side (about 10 minutes) and reheat at 300 for 10-15 minutes when ready to serve.
Cut into squares and dust with powdered sugar. Cool completely and wrap well if freezing. To reheat, cover with foil and place in 275° oven for 20-30 minutes. Removing foil for last 5-10 minutes.