Preheat oven to 350 °F (175°C)
Sift the flour, baking powder, baking soda, salt and spices together into a medium sized mixing bowl.
In a large mixing bowl, cream the butter with an electric mixer.
Add the eggs, egg whites, vanilla extract and the sweetener to the butter and continue mixing.
Add the pumpkin puree and continue mixing until thoroughly combined.
Add the sifted dry ingredients a scoop at a time mixing until all the ingredients are combined and you have a thick batter.
Grease and flour an 8 inch square baking dish
Pour the batter into the baking dish.
Using the back of a spoon or spatula, smooth out the batter, making sure it is evenly distributed in the pan.
Bake in the center of the oven for approximately 35 to 40 minutes, or until a toothpick inserted into the middle comes out clean.
Allow to cool completely if adding frosting.