Zucchini Gratin

1 tablespoon olive oil
4 cups sliced zucchini
1 onion, thinly sliced
2 scallions, chopped
1/2 cup grated sharp cheddar cheese
salt and pepper to taste
cooking spray
1/4 cup Panko (Japanese style bread crumbs)
2 tablespoons finely grated Parmesan cheese

Drizzle 1 tablespoon of olive oil in a fairly large saute pan over medium heat. Add the zucchini and cook until tender, tossing and stirring occasionally. When zucchini is just tender, remove from pan and place in a mixing bowl. Add the sliced onions to the saute pan and cook until they just begin to caramelize and turn a pale shade of brown (about 10 minutes on med-low). Add onion to the zucchini in the bowl.

Add scallions, cheddar cheese, salt and pepper to the zucchini and toss gently to combine everything. Spray a shallow baking dish with cooking spray and add the zucchini mixture to the pan. Preheat oven to 350ºF.

In a small bowl, combine the Panko and the Parmesan cheese. Sprinkle evenly all over the zucchini. Bake in the oven for about 30 minutes, or until the topping is evenly golden brown. Serve immediately.