To start, heat your olive oil over medium-high heat in a large saucepan or pot. Add the extra lean ground beef.
Cook the mince until it is browned and thoroughly cooked. When you're finished, remove the mince from the pan and set it aside.
Make the lasagna filling
Then, add the onion and sweat it for about 4-5 minutes until it becomes translucent.
Add the garlic, tomato paste, Italian seasoning, and diced bell pepper. Fry these for a minute while stirring.
Add the mince back into the pot. Stir the ingredients so the mince gets covered in the delicious flavorings.
Finally, add the remaining meaty sauce ingredients. That includes tomato sauce, crushed tomatoes, fresh chopped herbs, vinegar, and sugar. Don't go too heavy on the salt because the cheese will add more saltiness of its own.
Bring the sauce to a low simmer. Allow it to cook for 45 minutes while stirring constantly. When finished, your sauce shouldn't be dry but shouldn't have a ton of liquid either.
Assemble your baked lasagna
Preheat your oven to 350ºF (180ºC).
In a 9x13-inch baking dish, add 3 tablespoons of sauce. Spread it evenly on the bottom.
Add one layer of ready-to-bake lasagna sheets. Don't let them overlap. Cut the noodles to fit the uncovered spaces (if you have any).
Add a third of the sauce over the noodles. Make sure the layer is even and completely covers the noodles.
Sprinkle a generous layer of mozzarella over the sauce. Add half the ricotta cheese and sprinkle it over too. You can also sprinkle half of the grated parmesan now.
Add another layer of noodles over the cheese.
Add half of the remaining sauce on top of the noodles.
Next, add half of the leftover grated mozzarella, the rest of the ricotta cheese, and the remaining parmesan cheese.
Finally, add another layer of noodles. Add the leftover sauce and sprinkle all the remaining mozzarella cheese over it.
Bake the lasagna
Cover the baking dish with a layer of aluminum foil. Make sure it doesn't touch the cheese or sauce on the top layer. You can tent it slightly to prevent this from happening.
Bake the lasagna for about 35 minutes covered.
Then, remove the foil and continue baking it for another 10-15 minutes. This will allow the cheese to become melty and even a little charred.
Serve the lasagna immediately with your favorite side or beverage.