In a large skillet, heat the olive oil over medium-high heat. Sauté the chopped onion and garlic for about 1 minute, until fragrant and translucent. Add the ground beef and pork, cooking until no pink remains. Drain excess fat and season with salt and pepper. Stir in the tomato paste, diced tomatoes, sugar, basil, oregano, and red pepper flakes. Bring to a boil, then reduce heat and simmer uncovered for 15 minutes. Taste and adjust salt and pepper as needed.

In a medium bowl, mix the ricotta cheese, egg, basil, salt, and pepper until smooth. Set aside.

Boil the lasagna noodles in salted water until al dente, according to package instructions. Drain and lay flat on a clean towel to prevent sticking.

Preheat the oven to 350°F (177°C) and grease a 9×13-inch baking dish. Spread a thin layer of meat sauce on the bottom of the dish. Add 3 lasagna noodles, then layer with ⅓ of the meat sauce, ⅓ of the ricotta filling (in dollops), and 1 cup of mozzarella cheese. Repeat the layering process two more times, ending with the remaining mozzarella and a sprinkle of grated Parmesan on top.