How to Make It
Place an 8-inch round cake pan in oven. Preheat oven to 500°F (leave pan in oven as it preheats).
Bring a large saucepan filled with water to a boil over high heat. Add pasta; cook 8 minutes or until almost done; drain. Place eggs in a large bowl. Add hot pasta; toss to coat.
Heat oil in a large skillet over medium-high. Add sausage; cook 2 minutes or until browned, stirring to crumble. Add tomato, onion, and spinach; cook 7 minutes or until liquid has almost evaporated, stirring occasionally. Add sausage mixture to pasta mixture. Stir in pepper, salt, and 2 ounces cheese.
Carefully remove cake pan from oven; coat pan with cooking spray. Add pasta mixture to cake pan; sprinkle with remaining 1 ounce cheese. Bake at 500°F for 20 minutes. Remove pan from oven; cut spaghetti pie into 4 wedges.