Boil the spaghetti in boiling water.
Chop the onion and garlic.
Heat olive oil in a pan and sauté the garlic and onion.
Dice ripe tomatoes and add them to the pan, letting them simmer.
Add the cooked spaghetti noodles to the pan and toss them with the sauce.
Season with salt and pepper to taste.
Serve in a bowl and garnish with basil leaves.