Layers on Layers: Eggplant, Chickpea, and Tomato Casserole

medium eggplant, peeled or scored and sliced into ½ inch rounds

extra virgin olive oil + extra for eggplant

tomatoes, sliced into ~1/8 inch rounds

onion, cut in half and sliced into thin half-rounds

of chickpeas, drained and rinsed

tomato sauce