1 1/2 lb mozzarella cheese, cut into 1/4-inch slices
1 large white onion, cut into thin slices (optional)
Directions:
Cut the eggplant lengthwise once, then slice crosswise into semi-disks about 3/4 inch thick.
In a shallow casserole dish (about 2 in deep), stand some slices of eggplant on the narrow cut edge, to make a row, then follow this with slices of tomato, then slices of mozzarella cheese. Repeat until the whole dish is full. It should appear from the top to have bands of red, white and black.
Use your favorite seasoning (basil/oregano is the default), and bake until bubbly (about 25-30 minutes at 350 degrees F.