Start by preheating your oven to 375°F for the perfect bake.
Brown the ground beef in a saucepan over medium heat until no pink remains, about 5-7 minutes.
Add diced onion, 1 tablespoon oregano, the salt, and pepper to the beef, cooking until onions are tender.
Pour in marinara sauce and water, bring to a boil, then simmer to let flavors meld.
In a bowl, mix ricotta, eggs, Parmesan, remaining oregano, some extra salt, and pepper until combined.
Layer meat sauce, noodles, and cheese mixture in a 9x13-inch baking dish, ending with cheese on top, and finishing with the added mozzarella.
Bake the lasagna in the preheated oven until bubbly and noodles are tender, about 60 minutes.
Let the lasagna rest before serving to allow it to set for perfect slices.