Preheat to 375°F (190°C). Grease a baking dish so nothing sticks, including your hopes and dreams of a clean kitchen.
Brown the meat with onion and garlic in olive oil. Season with salt, pepper, and a little oregano if you’re feeling fancy. Drain excess fat.
Stir in marinara sauce and let it simmer a few minutes. It should smell like pizza night without the drama.
In a bowl, mix ricotta with the egg (if using) and a pinch of salt. This is your creamy binding agent, so don’t skip the pinch.
Cook the noodles if you’re not using no-boil. Boil until al dente, then drain. They’ll finish cooking in the oven anyway, so don’t overdo it.
Layer the lasagna in the dish: a thin sauce layer, noodles, ricotta mixture, meat sauce, mozzarella. Repeat. Finish with a final layer of sauce and mozzarella, plus parmesan on top.
Cover with foil and bake for 25 minutes. Then uncover and bake another 15 minutes until the cheese is bubbling and golden.
Let it rest 10–15 minutes before slicing. Resting = easier slices and less chaos when serving.