Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
   1      cup           chopped onions
   1                    chiles -- minced, to 2
   2      tablespoons   vegetable oil
   1      teaspoon      ground cumin seeds
   1      teaspoon      ground coriander seeds
   1      large         tomato -- chopped (about 1
                        -- cup)
   2      teaspoons     unbleached white flour
   1      cup           plain yogurt
                        salt to taste

Preparation:

Sauté the onions and chiles in the oil until tender, about 10 minutes. Add the cumin and coriander and sauté for a minute, stirring constantly. Stir in the tomato and flour and cook for 2 minutes. Finally, stir in the yogurt. Heat the sauce thoroughly, but do not allow it to boil or the yogurt will curdle. Add salt to taste and serve.