Heat olive oil or butter in a large pot over medium heat. Add garlic (and onion if using) and sauté until fragrant.
Add tomato sauce/crushed tomatoes, tomato paste, salt, pepper, and chili flakes. Stir well and cook for 1-2 minutes.
Pour in water or stock and add the uncooked pasta directly into the pot.
Let it simmer, stirring occasionally, until pasta is cooked and sauce begins to thicken.
Lower the heat and stir in cooking cream. Add a splash of reserved pasta water to adjust consistency.
Turn off heat and fold in fresh basil leaves. Mix well and let it rest for 1-2 minutes.
Serve hot and enjoy creamy, silky pasta straight from the pot.