SLICE THE TOMATOES into rounds a little less than 1/2-inch thick and dredge them in the cornmeal or flour. Heat enough oil in a 10-inch nonstick pan to cover the surface lightly and fry the tomatoes briefly on each side, until they are lightly colored. Do not let them get soft. Lightly beat the eggs with the scallions and basil and season them with salt and pepper. Pour them over the tomatoes. Let the eggs sit for about a minute, then give the pan a shake to loosen the bottom. Cook over medium-low heat until the eggs are nicely colored on the bottom, then slide the frittata out onto a large plate. Place the pan over it, invert and return it to the heat to cook the other side. Turn the frittata out onto a serving plate and serve, hot or tepid, cut into wedges.