Combine flour, baking powder, & salt in a bowl. Set aside.
Cream brown sugar, butter, eggs, & vanilla until light & fluffy making sure everything is combined well. Scrape bowl.
Gradually add flour mixture until just incorporated.
Press into a greased 9x13" pan (I used my mini rolling pin & rolled it flat using a little flour on my pin.) Combine sugar & cinnamon & sprinkle over the top.
Bake at 350*F for 25-30 minutes or until the surface springs back after a gentle push. Cool, cut & serve.