📝 About This Recipe
This vibrant gratin captures the essence of a sun-drenched garden in Southern France, layering tender zucchini and jammy tomatoes under a golden, herb-scented crust. Unlike heavier casseroles, this dish relies on the natural sweetness of peak-season produce and the sharp tang of Gruyère to create a sophisticated side or light vegetarian main. It’s a celebration of textures, ranging from the silky roasted vegetables to the satisfying crunch of garlicky sourdough breadcrumbs.
🥗 Ingredients
The Vegetables
- 3 medium Zucchini (sliced into 1/4-inch thick rounds)
- 5-6 pieces Roma Tomatoes (firm and ripe, sliced into 1/4-inch thick rounds)
- 1 large Yellow Onion (thinly sliced into half-moons)
- 3 cloves Garlic (minced)
- 3 tablespoons Extra Virgin Olive Oil (divided use)
The Gratin Topping
- 1 cup Sourdough Breadcrumbs (coarsely ground, preferably fresh)
- 1 cup Gruyère Cheese (freshly grated)
- 1/4 cup Parmesan Cheese (freshly grated)
- 1 teaspoon Fresh Thyme (leaves stripped from stems)
- 1/2 teaspoon Fresh Oregano (finely chopped)
- 2 tablespoons Unsalted Butter (melted)
Seasoning
- 1 teaspoon Kosher Salt (plus more for sweating zucchini)
- 1/2 teaspoon Black Pepper (freshly cracked)
- 1 pinch Red Pepper Flakes (optional for subtle heat)
👨🍳 Instructions
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1
Preheat your oven to 400°F (200°C). Lightly grease a 9x13 inch ceramic baking dish or a large oval gratin dish with a drizzle of olive oil.
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2
Place the zucchini rounds in a colander and sprinkle lightly with salt. Let them sit for 10-15 minutes to draw out excess moisture; pat them dry with paper towels. This prevents a soggy gratin.
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3
Heat 1 tablespoon of olive oil in a skillet over medium heat. Add the sliced onions and a pinch of salt. Sauté for 8-10 minutes until soft and translucent, but not browned.
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4
Stir the minced garlic into the onions and cook for just 1 minute until fragrant. Remove from heat and spread the onion-garlic mixture evenly across the bottom of the prepared baking dish.
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5
In a small bowl, combine the breadcrumbs, melted butter, grated Gruyère, Parmesan, thyme, and oregano. Mix until the crumbs are evenly coated and clump slightly.
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6
Layer the vegetables: Arrange the zucchini and tomato slices in the dish by alternating them in rows, overlapping them slightly like shingles (shingling). Stand them up slightly for a beautiful presentation.
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7
Drizzle the remaining 2 tablespoons of olive oil over the arranged vegetables and season evenly with the kosher salt, black pepper, and red pepper flakes.
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8
Cover the dish tightly with aluminum foil and bake for 20 minutes. This steams the vegetables slightly, ensuring the zucchini is tender.
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9
Remove the foil and sprinkle the breadcrumb and cheese mixture evenly over the top of the vegetables.
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10
Return the dish to the oven, uncovered, and bake for another 20-25 minutes. The vegetables should be bubbling and the topping should be a deep golden brown.
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11
If the top isn't as crunchy as you'd like, turn on the broiler for 1-2 minutes, watching very closely to prevent burning.
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12
Remove from the oven and let the gratin rest for 5-10 minutes before serving. This allows the juices to settle and makes it easier to scoop.
💡 Chef's Tips
Always salt and drain your zucchini slices first to avoid a watery dish. Use high-quality, block Gruyère and grate it yourself for the best melting capability. If your tomatoes are very watery, gently squeeze out the seeds before slicing. For a gluten-free version, swap the sourdough crumbs for almond flour mixed with extra Parmesan. Try to use zucchini and tomatoes of a similar diameter for a more uniform and professional look.
🍽️ Serving Suggestions
Serve alongside a grilled Ribeye steak or roasted chicken for a complete meal. Pair with a crisp, chilled Provencal Rosé or a light Sauvignon Blanc. Accompany with a simple green salad dressed in a sharp lemon vinaigrette. Serve as a light lunch with a thick slice of crusty baguette to soak up the juices. Top with a few fresh basil leaves just before serving for an extra pop of color and aroma.