Spray the eggplant on both sides with nonstick spray and season with salt and pepper.
Grill the eggplant on both sides until it starts to soften. Remove from heat.
Build the eggplant tower: slice of eggplant, cheese, tomato seasoned with salt, slice of eggplant, cheese, tomato seasoned with salt, slice of eggplant. (repeat for the number of portions you have)
Place back on the grill on the top rack or on the side of the grill that is not lit to melt the cheese before serving. (Alternatively place on a baking sheet in a 350 degree oven to melt the cheese)