Cut onion into cubes and sauté in oil until translucent. Briefly fry the rice. Heat tomato sauce and add.
Cook with the lid on low heat until the rice is ready. Stir again and again. If necessary, add hot water.
Cut tomato into pieces and mix in 1 minute before rice is done. Add cayenne pepper and sugar.
Stir in cheese and season to taste. Sprinkle the risotto with Parmesan cheese at the table.