Preheat the oven to 350 degrees. Grease a 9 x 13 pan.
In a medium bowl combine the flour, baking powder, salt, and apple pie spice.
In a large bowl mix together the melted butter, brown sugar, and white sugar. Stir in the eggs and vanilla. Mix well.
Blend the flour mixture into the butter mixture and mix until just combined. Stir in the apples.
Spread the mixture evenly into the pan. Bake for 30-40 minutes or until the top is golden brown and a toothpick inserted into the center comes out clean.
Remove from the oven and cool completely on a wire rack before cutting into squares.