Prepare the Pancetta: Heat a nonstick skillet over medium heat and add a small amount of vegetable or olive oil. Once hot, add the diced pancetta and cook until the fat renders and the pancetta becomes crispy.
Cook the Aromatics: Add the diced onion and minced garlic to the skillet. Continue to cook until the pancetta is deep golden, and the onions and garlic are soft and fragrant. Do not drain the fat, as it adds significant flavor to the sauce.
Add Tomatoes: Incorporate the roasted tomato halves or chopped tomatoes into the skillet. Let them simmer for about 5 minutes until they break down and form a saucy consistency.
Create the Sauce: Pour in the single cream and gradually add water to achieve the desired sauce consistency. Stir well to combine.
Incorporate Spinach: Add the spinach to the skillet and stir until it wilts. Let the sauce simmer briefly until the spinach is well-coated and the sauce is silky. Season with salt and pepper to taste.
Combine with Pasta: Toss in the cooked pasta, ensuring it's evenly coated with the sauce. Long noodles like tagliatelle or spaghetti work well, but short noodles like penne also complement the dish.