In a large pot of boiling water, cook the pasta until tender, but firm. Drain and return the pasta to the pot.
While the pasta is cooking, heat the oil over medium heat in a non-stick pan. Cook the sausage until it is just a bit pink in the centre, about 15-20 minutes. Drain well and cut it into thin round slices. Cook the onion until tender, about 5 minutes. Add the garlic, tomatoes, basil, oregano and the sausage slices. Simmer uncovered for 10 minutes. Pour the mixture over the cooked and drained pasta and toss to mix it all together.