1 tablespoon curry powder
7 1/2 tablespoons olive oil
1 1/4 cups whole-wheat or regular panko bread crumbs
2 teaspoons coarse kosher salt
1 large white onion, halved and thinly sliced
2 teaspoons finely chopped rosemary
1 pint cherry or grape tomatoes, halved
1/4 cup dry white wine
2 garlic cloves, minced
1 teaspoon orange zest
1/2 teaspoon black pepper, more to taste
4 medium zucchini (about 1 1/2 pounds), thinly sliced (about 7 cups)
Heat oven to 400 degrees. Heat a large skillet over medium-high heat, then add curry powder and let toast until fragrant, about 30 seconds. Add 2 tablespoons olive oil, then stir in panko bread crumbs and 1 teaspoon salt. Cook for 2 to 3 minutes, stirring occasionally. Transfer to a bowl and wipe out skillet.
In the same skillet, heat 2 tablespoons olive oil over high heat, then add onions, rosemary and 1 teaspoon salt. Cook for 10 to 15 minutes, stirring often, until onions are a deep golden brown. Add tomatoes and cook for another 5 minutes. Pour white wine into pan and bring to a simmer, scraping up any brown bits. Remove from heat and stir in garlic, orange zest and black pepper.
Grease inside of a medium-size gratin dish with 1/2 tablespoon olive oil and spread a third of the onion and tomato mixture on the bottom. Begin layering zucchini in an overlapping pattern, beginning around the outside and working your way in. Sprinkle with a third of the bread crumbs. Repeat layering two more times, ending with bread crumbs. Drizzle 3 tablespoons olive oil over bread crumbs and bake for 1 to 1 1/2 hours, or until vegetables are extremely tender and top has browned.