Put a little oil in a pan and add the onion. Cook until golden brown.

Add the bacon pieces and cook until browned.

Separately, bring water to a boil and add the spaghetti once boiling.

When the bacon is browned, add the heavy cream and salt to taste.

Let the cream thicken, and when it thickens, add pasta cheese or Parmesan.

Let it thicken, and when the spaghetti is done, mix it with the sauce.