In a large saucepan, heat the oil over high heat and add the garlic, onion, pepper, and tomato puree. Lower the heat to medium, and add the rice and water. Bring to a boil. Right at the boiling point, lower heat, cover, and allow it to cook slowly for about 20 minutes. Add the corn, and simmer for another 10 minutes.
Fluff rice, garnish with lemon slices, and serve.