Cook the bow tie pasta according to package instructions in a large pot of salted boiling water until al dente. Drain and set aside.

In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté for about 3-4 minutes until softened.

Add the minced garlic to the skillet and cook for an additional 1 minute until fragrant.

Remove the casing from the Italian sausage and add the sausage to the skillet. Cook, breaking it apart with a spoon, until browned and cooked through, about 5-7 minutes.

Stir in the diced tomatoes (with their juice), dried basil, and dried oregano. Season with salt and pepper. Simmer for about 5 minutes to allow the flavors to meld.

Add the cooked bow tie pasta to the skillet and toss to combine with the sausage mixture.

Remove from heat and sprinkle the shredded mozzarella and grated Parmesan cheese over the top. Cover the skillet for a few minutes until the cheese melts.

Serve hot, garnished with fresh basil leaves if desired.