Boil a large pot of salted water and cook spaghetti according to package instructions.
While the pasta cooks, heat olive oil in a large skillet over medium heat.
Add chopped onion and minced garlic to the skillet, sautéing until soft.
Increase heat and add ground beef, cooking until browned.
Stir in canned tomatoes and tomato paste, mixing well.
Add oregano, salt, and pepper, simmering for 20 minutes.
Drain the spaghetti and add it to the sauce, tossing to coat evenly.
Serve hot, garnished with fresh basil and grated Parmesan cheese.