Bring a large pot of lightly salted water to a boil. Add the spaghetti, and cook until al dente, or 8 to 10 minutes. Drain, and rinse under cold water. Toss with a drizzle of olive oil, cover, and keep warm.

Place 2 tablespoons olive oil in a skillet over medium heat. Stir in the onion, and cook until soft and transparent, about 5 minutes. Add the sardines; cook and stir 5 to 8 minutes until the sardines start to break apart. Mix in the tomatoes, and cook until mixture is heated through. Stir in the bread crumbs. Serve over spaghetti, and top with desired amount of grated Parmesan cheese.