Cook the pasta in salted water for 10-12 mins until al dente. Meanwhile, heat the oil in a medium pan. Add the sliced onion and pepper and fry, stirring frequently for 10 mins until golden. Stir in the garlic and spices, then tip in the tomatoes, half a can of water, the corn and bouillon. Cover and simmer for 15 mins.
Meanwhile, toss the avocado with the lime juice and zest, and the finely chopped onion.
Drain the penne and toss into the sauce with the coriander. Spoon the pasta into bowls, top with the avocado and scatter over the coriander leaves.