Slice the eggplant into 1cm thick pieces.
Sprinkle with salt and let sit for 10 minutes, then remove excess moisture.
Finely chop onion and garlic.
Sauté the eggplant in a pan with olive oil until golden brown.
Sauté the onion and garlic.
Add tomato sauce and bring to a simmer.
Layer the eggplant, sauce, and cheese in a gratin dish.
Bake in a 200°C oven for 15 minutes.