Preheat oven to 350°F. Prep a 9" x 13" baking pan with nonstick baking spray. Line the baking dish with parchment paper. Make sure that the parchment paper overhangs on the sides of the baking dish. (This ensures the brownies can be taken out of the pan easily.)
In a large mixing bowl, use a hand mixer to beat the melted butter, light brown sugar, and 1 ½ cup of sugar until combined.
To the melted butter mixture, add the eggs, vanilla extract, cinnamon, salt, and baking powder. Beat to mix into a creamy texture.
Gently beat in the flour at a low speed. Switch to use a large spoon or your hands to completely mix all of the ingredients. (Your batter will be extremely thick.)
Add in the apples. Gently stir to mix well.
Add in the chopped pecans. Stir to mix in. (You may want to use your hands to fully mix all of the ingredients.)
Scoop the batter in the prepared baking dish. With an offset spatula even the top of the batter out.
Sprinkle the batter with the sugar/ cinnamon topping.
Bake at 350 degrees for 40-45minutes.(Insert a toothpick in the centerof the dish. If it comes out clean then it is done, if not then return it tothe oven. )
Remove from the oven and allow to cool in the baking dish prior to cutting into bars.