1 medium-large zucchini, trimmed, split lengthwise, and cut crosswise into 1/2-inch slices
2 small yellow squash, split lengthwise, and cut crosswise into 1/2-inch slices
1 small yellow onion (or half of a medium-large), peeled, halved, and cut into 1/4-inch slices
Sea salt to taste
Freshly ground black pepper to taste
Red pepper flakes to taste
3 tablespoons nutritional yeast
1 tablespoon vegan butter (I like Earth Balance)
1 tablespoon olive oil
1 cup Panko bread crums (any bread crumb will do, but I love the crunchiness of Panko)
3 tablespoons finely chopped fresh herbs (I use equal parts sage, basil and oregano, but use what you have)
Preheat oven to 450 degrees. Oil a 9-inch glass or ceramic pie dish with non-stick spray (or olive oil). Add both squashes, drizzle with a little more olive oil, sprinkle with salt, pepper, and red pepper flakes. Toss and then spread to an even layer. Top with sliced onion and sprinkle with additional salt, pepper and 1 tablespoon of the nutritional yeast. Cover with foil and bake for 20 minutes. Meanwhile, stir together the melted butter, olive oil, bread crumbs, remaining 2 tablespoons of nutritional yeast and herbs. After the vegetables have cooked for 20 minutes, remove the foil from the dish, sprinkle the top of the veggies evenly with the bread crumb mixture, and return to the oven for 10 minutes. I like the top very brown and crispy, but if you prefer less color and crunch, simply remove the gratin from the oven after about 8 minutes. Serve immediately or at slightly warmer than room temperature.
Note: this dish is also delicious with 1/4-inch thick slices of tomatoes (from a cored medium-large tomato) arranged over the top of the onion before the vegetables are sprinkled with the bread crumbs.