Heat the oven to 400°F. Boil spaghetti in water with the tablespoon salt until 2 minutes short of the package time. Drain, toss with 1 tablespoon oil and spread in a large bowl to cool for 5 minutes.
Beat eggs with Parmesan and toss thoroughly through the warm, not steaming, noodles. Grease a 9-by-13-inch metal baking pan with remaining oil and press spaghetti into an even base.
Bake the base for 12 minutes until starting to set. Mix tomato sauce with oregano and garlic powder.
Spread seasoned sauce over the base and scatter with mozzarella, pepperoni and olives. Bake for 15 to 18 minutes until the topping bubbles and the center reaches 165°F.
Rest for 10 minutes and cut into 8 squares with a wide spatula.