Slice the tomatoes 1/4-inch thick. Lay them out in a shallow baking pan and sprinkle with salt. Place the tomato slices in a colander and allow time for salt to pull the water out of the tomatoes, approximately 30 minutes.
In a skillet, heat the oil for deep-frying over medium-high heat.
Dip the tomatoes into buttermilk, then dredge them into flour with a dash of pepper. Deep-fry until golden brown. Keep warm.
For the Vidalia Onion Relish: Mix all ingredients together in a bowl. Cover with plastic wrap and let marinate for a few hours.