HEAT OLIVE OIL in a nonreactive skillet. Add tomatoes, peppers, olives, half teaspoon salt and several grindings of pepper; mix well. Cover and cook over medium heat 10 minutes, stirring occasionally. Off heat, set sauce aside until pasta is ready. Bring 4 litre water to a boil with 1 tablespoon salt. Add spaghetti and cook until slightly less than al dente. Return sauce to a simmer. Drain pasta and add it to sauce. Toss over medium heat 30 seconds, then add cheese and toss once more. Serve at once.