Preheat your oven to 350 degrees F. Spray an 11x17 inch pan generously with nonstick spray. Sprinkle a couple teaspoons of flour over the pan, then shake it around the edges and tap the excess into the sink. This keeps your cake from sticking to the pan.
In a large bowl or stand mixer, beat together eggs.
Add sugar, oil, melted butter, and pumpkin. Beat well for about 2 minutes until fluffy, scraping down the sides and bottom.
Add the flour but don't stir.
Make a small well in the flour and add the baking soda, baking powder, salt, pumpkin pie spice, and cinnamon. Use a small spoon to blend these in with the flour.
Use the beater to mix in the flour.
Beat well, scraping sides and bottom.
Pour into the prepared pan and smooth top.
Bake at 350 for about 20-25 minutes. A toothpick inserted in the center should come out dry, meaning there is no batter on it.