Preheat oven to 400 degrees Fahrenheit (200 degrees Celsius).

Brush red and yellow peppers and eggplant slices with olive oil. Season with kosher salt and pepper to taste and roast on a baking sheet for 30–40 minutes, until soft but not browned.

Meanwhile, sauté zucchini, onions, and garlic in olive oil in a large frying pan. Season with salt and pepper to taste.

In an eight-(20-cm) or nine-inch (23-cm) round springform pan or a disposable round pan, place each vegetable in a single overlapping layer, sprinkling cheese, salt, and pepper between each layer. Begin with half of the eggplant, then half of the zucchini-onion-garlic mixture. Continue with the red peppers and yellow peppers, then the rest of the zucchini-onion-garlic mixture, ending with the eggplant.

Cover the vegetables with a six-inch (15-cm) round piece of parchment paper. Then place a six-inch (15-cm) disc (another cake pan or the false bottom of tart pan) on top. Weigh it down with jars or cans.

Place pan onto a cookie sheet (it will leak) and chill completely the day before you need it.

Drain the liquid. Serve on a platter at room temperature.