Wash your hands well with soap and warm water for at least 20 seconds.
Spray baking pan with vegetable oil cooking spray.
Wash tomatoes and cut into slices, about ¼-inch thick.
Crack egg into small bowl, add buttermilk, and mix together with a fork or whisk.
In another small bowl, add cornmeal, cayenne pepper, garlic powder, pepper, and salt and mix together with a fork. Dip each tomato slice into the buttermilk and egg mixture, let excess liquid drip off. Then dip the slices into the cornmeal mixture. Turn and press slices to coat evenly and gently shake off excess.
Arrange tomato slices on baking pan. Spray top of tomato slices with vegetable oil cooking spray. Place pan in oven. After 15 minutes, spray the top of the tomato slices with vegetable oil cooking spray and turn tomato slices. Bake an additional 15 minutes.