Created by Under15Cook on June 23, 2014
Step 1: CAKE: Stir 1 tablespoon softened butter and white sugar together in a coffee mug until fluffy; stir egg, sour cream, and vanilla extract into the butter mixture. Add 1/4 cup flour and baking powder into the mixture stir until smooth.
Step 2: TOPPING: Mix 2 tablespoons flour, brown sugar, and cinnamon together in a bowl. Mash 1 tablespoon butter into the flour mixture with a fork or pastry cutter until mixture is crumbly; sprinkle over the cake batter in mug.
Step 3: Cook in a microwave oven on high for 1 minute. Continue cooking in 10 second intervals until a toothpick inserted into the middle comes out clean.