Preheat the oven to 350 degrees. Spray an 8-inch springform pan or a 9 inch deep-dish pie plate with cooking spray.: The warm oven smell that fills the kitchen as it reaches 350 degrees signals the transition from prep to baking. You should notice a faint, clean warmth and a sense of readiness when the temperature is steady. Preheating matters because it ensures the pie starts baking immediately and the cheese melts uniformly, creating a nice top crust. A common error is sliding the pie into an oven that is still heating, which can lead to uneven melting and a soggy center. If you’re unsure about your oven temperature, use an oven thermometer for accuracy.
Cook the pasta in a large pot of salted, boiling water for 6 to 7 minutes or until almost al dente. (The pasta will continue cooking in the oven.). Drain and set aside.: As the spaghetti hits the water, listen for a lively, rolling boil and watch the strands soften and float. The pasta should be slightly firm in the center since it will continue to soften in the oven. This partially cooked stage prevents the pie from becoming mushy. Overcooking here will cause the strands to break down and create a gummy texture, so test a piece for a slight bite before draining. Salt the water generously so the pasta itself carries seasoning.
In a large skillet, brown the ground beef over medium heat until no longer pink, approximately 4 to 5 minutes. Transfer to a bowl using a slotted spoon and discard the fat from the pan (leave a couple teaspoons for sauteing the onion).: When you add the ground beef to a hot skillet, you should hear a steady sizzle and see the meat release juices. Browning creates complex flavors through caramelization, giving the pie a robust savory base. Cook until there is no pink and the edges begin to color, about four to five minutes, then remove with a slotted spoon and discard most of the fat. Leaving too much fat will make the final texture greasy, so drain well but leave a couple teaspoons for sautéing the onion .
Return the pan to the heat and cook the onion until softened, approximately 3 to 4 minutes. Add the garlic to the pan and cook for 1 minute. Stir in the Italian seasoning and onion powder. Remove from the heat and set aside.: With the reserved fat, return the pan to medium heat and add the diced onion . You will notice the onion go translucent and release sweet aromatics as it softens, which takes about three to four minutes. Add the minced garlic and cook for one minute until fragrant, avoiding browning so it stays sweet rather than bitter. Stir in the Italian seasoning and onion powder so their oils bloom in the warm pan. A frequent pitfall is letting the garlic burn, which can impart a harsh flavor, so watch closely during this step.
In a large bowl, whisk together the sauce, ricotta cheese, parsley and eggs. Stir in the onion mixture.: As you combine the marinara sauce , ricotta cheese , chopped parsley, and eggs in a bowl, notice the change in texture from separate elements to a cohesive, creamy mixture. Whisking smooths the ricotta and helps the eggs distribute evenly, which creates a custard like hold when baked. This binding mixture is essential for structure, so take a moment to ensure it is homogenous. If the mixture is lumpy, your pie may not set properly, so whisk until silky.
Toss the pasta and beef with the sauce mixture to combine. Stir in 1/2 cup parmesan and 1/2 cup mozzarella. Transfer the spaghetti mixture to the prepared pan. Sprinkle the remaining cheese over the top.: When you fold the warm spaghetti and browned ground beef into the sauce, feel the strands become slick and glossy as they absorb the mixture. Stir in half of the Parmesan and half of the Mozzarella so pockets of cheese hide within the pie. Transfer the combined mixture into the greased pan, pressing gently to compact the strands into a sliceable shape. Sprinkle the remaining cheeses on top so they melt into a golden, bubbling crown. A common mistake is packing the pan too loosely, which can cause the pie to fall apart when sliced; press firmly but gently so it holds together.
Bake until the cheese is melted and bubbling, approximately 25 to 30 minutes. Remove from the oven and allow to rest for 5 minutes before cutting and serving.: As the pie bakes, you will see the top turn golden and the Mozzarella begin to bubble vigorously, releasing a warm, toasty aroma. The oven’s heat finishes cooking the pasta and sets the egg enriched filling. Baking for the full time ensures the center is warmed through and the edges develop a slight crisp. Removing it too early can result in a floppy interior, while leaving it too long may dry out the pie, so watch for the visual cues of bubbling and browning. Allow it to rest for five minutes after baking so the interior firms, making clean slices easier to cut.