For the fried green tomatoes: In a large, heavy-bottomed skillet heat about 3/4-inch oil until a pinch of cornmeal tossed in bubbles vigorously, about 5 minutes.
Meanwhile, combine the cornmeal, flour, garlic powder, paprika, white pepper and salt in a medium bowl with a whisk. Dredge the tomato slices in the seasoned flour and add to the skillet (do not crowd). Cook, flipping once, until the tomatoes are golden, about 6 minutes total. Repeat with the remaining tomatoes.
Serve the tomatoes with the grits.