Cook the pasta as you like it, or according to the package directions, cooking it slightly under so that it finishes in the sauce.
Meanwhile, in a large skillet, cook the bacon until the fat is starting to render off; add the onion and sauté until the onion is soft and the bacon is crispy. Drain off half of the bacon fat and reserve it for other use.
Add the tomatoes and cook until the tomatoes break down and the sauce thickens. Add the chili powder to taste (half a tablespoon?) and some salt and pepper. If it gets too thick, you can thin it with a little of the hot pasta cooking water, straight from the pot, or a splash of stock.
Drain and add to the skillet; toss to coat and serve topped with Parmesan. Serves 2-4.