Heat chopped onions and garlic until golden brown in hot fat. Mix
flour with fat. Add tomato paste, water, oregano and salt. Cook to
consistency of a gravy, about 15 minutes. Hint: Chiles rellenos may
be prepared ahead of the meal, cooked, and stored in the
refrigerator. When read to use, add the sauce and the grated cheese.
Place in 325 oven for 30 minutes (or until cheese melts).