Boil spaghetti in salted water until al dente; drain.
Blanch and blend tomatoes into a puree.
Heat olive oil in a skillet, sauté diced onion and garlic paste for 2 minutes, then add ground beef and cook until browned.
Pour in tomato puree, dried oregano, black pepper, and salt; simmer for 15 minutes.
Toss cooked spaghetti in the meat sauce and serve topped with parmesan cheese.