Slice tomatoes into 1/4-inch-thick slices. In a pie plate or baking dish combine cornmeal, flour, sesame seed, onion salt, and pepper. In a small mixing bowl combine egg and milk. Dip tomatoes slices into egg mixture, then coat both sides of tomato slices with the cornmeal mixture.
In a heavy large skillet heat about 1/4 inch of cooking oil over medium heat. Fry tomato slices in a single layer about 2 minutes on each side or until golden brown. Drain on paper towels. Keep slices warm in a 300 degree F. oven while frying remaining tomatoes. Serve immediately. Makes 4 to 6 servings.