Cook spaghetti according to package instructions; drain and set aside.

In a large skillet, heat olive oil over medium heat. Add chopped onion and minced garlic, sauté until onion is translucent.

Add ground beef to the skillet and cook until browned. Drain excess fat if necessary.

Stir in diced tomatoes, tomato paste, Italian seasoning, salt, and black pepper. Simmer for 10 minutes.

Combine the cooked spaghetti with the sauce in the skillet. Toss to coat evenly.

Serve topped with grated parmesan cheese and fresh basil.