Tempura Batter for Vegetables

1 cup flour
1/4 cup cornstarch
1 teaspoon baking powder
1 teaspoon salt
1 egg, slightly beaten
3/4 cup cold water
1/4 cup vegetable oil
Cayenne pepper, to taste (optional)

Mix together dry ingredients. Add egg, water and oil and cayenne pepper, if desired. Stir to blend. Use to dip slices of yellow squash, zucchini, eggplant, green tomatoes, onion rings, mushrooms or fish fillets for frying. Fry in small bit of oil in skillet or wok on very high heat. Batter will keep, covered, in refrigerator for a few days.