Prepare the sauce base: Heat enough oil in a pan over medium heat. Add chopped onion and fry, stirring constantly, until evenly browned, about 7 to 8 minutes.
Add garlic and spices: Add chopped garlic, dried oregano, and ground black pepper to the browned onion. Stir and cook for about 1 minute to avoid burning the garlic.
Add tomato puree: Add the canned tomato puree (which contains salt) to the pan. Lower heat to medium to medium-low and sauté the sauce.
Cook the spaghetti: In a separate pot, boil water with 2 teaspoons of salt. Add the 200g spaghetti and cook for about 10 minutes until al dente. Drain and shake off excess water.
Combine spaghetti and sauce: Add a little of the spaghetti cooking water to the tomato sauce and stir. Cook for 1 more minute to ensure garlic is well cooked.
Finish cooking: Add the drained spaghetti to the sauce. Cook over medium heat for 7 to 8 minutes, allowing the spaghetti to absorb the sauce flavor and brown slightly.
Serve: Once the spaghetti looks slightly golden, it is ready to serve. Adjust seasoning if needed.