Heat the oil in a saucepan or deep frying pan. Add the hot pepper flakes, and cook for a few seconds, stirring to prevent them from burning. Add the strips of red pepper and cook gently , covered, for about 10 minutes, until they start to soften. Add the tomatoes, breaking them up with a wooden spoon, and stir in tomato puree. Bring to a boil, lower heat, and simmer, uncovered, for about 30 minutes, stirring occcasionally. Add the olives and capers, and cook 5 minutes more. Season to taste with salt and pepper. Meanwhile, cook pasta in boiling salted water until al dente. Drain the pasta and serve immediately with sauce