Season the green tomatoes with the salt and pepper. Combine the cornmeal and flour. Heat a large cast-iron pan over medium heat. When hot, add olive oil to coat (about 1/3 cup for a 12-inch pan). Dust the tomatoes in the cornmeal mixture just before you put them in the pan. Don't crowd them. Cook the tomatoes, in batches if necessary, until well browned on both sides (3 to 4 minutes per side); add more oil if needed. Drain on paper towels and serve warm, sprinkled with extra salt if you like.