.Heat grill to medium.
Spread eggplant slices on 2 baking sheets or trays. Brush 1/4 cup oil over both sides of eggplant slices. Spray another baking sheet with cooking spray and arrange tomato slices onit.
Season eggplant and tomatoes with pepper.
Oil the grill rack. Grill the eggplant slices until browned and tender, 5 to 7 minutes per side.
Set aside. Place the baking sheet with tomatoes on the grill rack; cover and grill until tomatoes are bubbling and warm, about 7 minutes.
Preheat oven to 350°F Spray six 7-10 oz ramekins ar custard cups 9 about the sane size as eggplant slices) with cooking spray.
Assemble the towers. Using a wide spatula, layer an eggplant slice, a tomato slice, and a basil leaf in each ramekin. Sprinkle with about 1 tablespoon of feta. Repeat the layering once more, then top with an eggplant slice. Press down lightly.
Place ramekins on a baking sheeet and bake until heated through and juices are bubbling around the edges. 25 to 35 minute.
To serve, run a paring knife around the sides of each ramekin. Invert a plate on top and, grasping ramekins and plate with oven mitts, carefully invert the ramekins onto a plate. Very hot. Drizzle the tower with a little oiland garnish with basil sprig. Serve hot , warm or at room temperature.