Pre-heat oven to 350 degrees F. Spray a 9x13 baking dish with non-stick cooking spray; set aside.
Using a stand mixer or hand mixer, cream together butter and brown sugar until light and fluffy, about 5 minutes. Add eggs one at a time, making sure to incorporate each one.
Add vanilla and beat until smooth.
Add baking powder, salt, cinnamon, nutmeg and flour to a medium bowl; whisk to combine. Add the flour mixture to the mixer and stir until just combined.
Pour batter into baking dish and spread evenly with a spatula.
In a small bowl mix cinnamon and sugar. Sprinkle evenly over the batter.
Bake for 25-35 minutes or until bars are set in the middle and a toothpick inserted in the middle comes out clean. Cool completely until cutting into bars.
Eat by themselves or with a dollop of vanilla ice cream. Enjoy!