Sauté the onion and peppers for 2-3 minutes until the onion is translucent. Add beef and garlic, and cook until the meat no longer looks red. Season with ground cumin and salt, to taste. Add tomato puree, tomatoes and water. Cover the frying pan and lower the heat. Let simmer, stir occasionally and let cook for 15-20 minutes, or until the meat is completely cooked and tender.