Cook spaghetti in salted water until al dente. Meanwhile, peel and coarsely chop the onions and carrots and briefly chop in a food processor.
Heat olive oil in a saucepan and brown the minced meat with the vegetables. Season with salt, pepper and oregano. Puree the pelati with a hand blender and add together with the ketchup. Cook for about 8 minutes.
Stir in parsley and season again with salt and pepper. Strain spaghetti and arrange on warmed plates. Spread the sugo over the top and sprinkle with grated Parmesan cheese.