Preheat to 350°F and grease a 9x13 dish

In a medium bowl, whisk flour, baking powder and salt

In a large bowl, beat brown sugar, butter, eggs and vanilla until smooth. add flour mixture and beat until well blended

Spread batter evenly in the pan

In a small bowl mix sugar and cinnamon and sprinkle evenly over the whole thing

Bake 25-30 minutes