Preheat the oven to 350 degrees. Slice the eggplant, zucchini, summer squash, and tomatoes crosswise into ½-inch thick slices. Heat the oil in a large skillet over medium-high heat. In batches, add the eggplant slices and cook, flipping once, until both sides are golden brown, about 5 minutes. Drain on paper towels and sprinkle with salt.
Oil a large baking dish or tian. Make a pinwheel pattern of the eggplant, zucchini, summer squash and tomato slices, layering in the onions and garlic, until all the vegetables are used.
Whisk together the eggs, cream, parmesan, basil and red pepper, season with salt and pepper, and pour into the baking dish. Bake the tian until the vegetables are tender, the custard is set, and the top is nicely browned, 45 minutes to 1 hour. Serve right from the baking dish.
I continued baking this a little past this stage where we took the photo. Cook it for the full 45 minutes to 1 hour, until it looks more browned than it does in this photo.
Also, pictured here, is a half recipe. Served 2.
Recipe by Love and Lemons at https://www.loveandlemons.com/eggplant-summer-squash-tian/