Preheat oven to 350°. Line a 9x9 baking pan with parchment paper or spray liberally with nonstick cooking spray. Set aside.
In a medium bowl combine melted butter and brown sugar. Use a spoon to combine the ingredients until thick. Add the egg and vanilla, continue to mix until completely incorporated.
Add the cinnamon, nutmeg, salt, baking powder and flour to the wet ingredients and stir until mixed well. Finally, add in the shredded zucchini and stir until it is evenly distributed. NOTE: If your zucchini is super watery, place it in a double lined paper towel and squeeze some of the water out over a sink.
Pour the batter into your prepared pan and bake for 18-22 minutes, being sure to not over bake.
Remove from the oven and allow the bars to cool completely on a cooling rack.