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Zucchini and Onion Gratin

Course Side Dish
Cuisine American
Servings 4 people


  • 3 zucchini diagonally sliced into 1/4"-thick pieces
  • 1 large onion thinly sliced
  • 2 Tbsp tomato paste
  • 2 tsp lemon zest
  • 1/4 cup Parmesan cheese
  • 1 tsp fresh thyme
  • olive oil
  • salt & pepper to taste


  1. Heat a large skillet over medium heat. Add 1 tablespoon of oil to the pan; swirl to coat. Add sliced onions and cook for 6 minutes, stirring occasionally. 

  2. Stir in tomato paste and cook for 2 minutes. Stir in lemon zest and thyme, season with salt and pepper, and cook for an additional 2 minutes, stirring occasionally.

  3. Preheat the broiler and arrange zucchini on the broiler pan. Drizzle with about 1 tablespoon of oil, season lightly with salt, and toss to coat. Broil for 7 minutes or until lightly charred. 

  4. Preheat oven to 375°. Spread onion mixture in a 2-quart gratin/casserole dish. Then arrange zucchini over onion mixture. Sprinkle with cheese; cover, and bake for 25 minutes. Remove from the oven.

  5. Preheat boiler and uncover zucchini pan. Broil for a few minutes or until lightly browned. Serve warm or at room temperature.