from Vegetarian Cooking for Everyone
2 Tbsp vegetable oil
2 Tbsp finely diced onion
1 large garlic clove, finely chopped
1 tsp dried oregano, optional
2 Tbsp flour
1/2 tsp ground cumin, optional
1/2 cup ground red chile
salt
Heat the oil with the onion, garlic, and oregano in a heavy saucepan. Cook over medium heat until the onion begins to color a little, about 6 minutes. Add the flour and cumin and cook for at least 2 minutes, stirring constantly. The flour will brown slightly. Mix the chile and 2 1/2 cups warm water and pour it all at once into the roux, whisking as you do so. Keep stirring until the sauce thickens, then lower the heat and cook, stirring occasionally, for 15 minutes. Season with salt to taste. If it tastes a little hars, just a few drops of vinegar will soften it.