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5 from 8 votes

Make-Ahead Vegetable Tian

Make-Ahead Vegetable Tian is as delicious to eat as it is beautiful to present. Imagine layered alternating potatoes, zucchini and tomatoes sitting atop luscious caramelized onions topped with Gruyère cheese. The vegetable tian is the perfect side dish to serve for a special occasion or anytime for that matter. What's even better is that the leftovers, if any are just as amazing.
Prep Time15 minutes
Cook Time1 hour 30 minutes
Salting Time30 minutes
Total Time2 hours 15 minutes
Course: Side Dish
Cuisine: French
Servings: 6 servings
Calories: 255kcal


  • 1 ¼ pounds onions, sliced (2 large onions)
  • 2 Tablespoons olive oil
  • 2 cloves garlic, minced
  • 1 ¼ pounds Yukon Gold potatoes, peeled and sliced ¼-inch thick (See Tip 1)
  • 1 large zucchini (12 - 14 ounces), sliced ¼-inch thick (See Tip 1)
  • 6 Roma tomatoes (1 ¼-pounds), sliced ¼-inch thick (See Tip 1)
  • 5 ¾ teaspoons Kosher salt, divided (See Tip 2)
  • ½ teaspoon dried thyme, divided
  • ½ teaspoon freshly ground black pepper, divided
  • ¼ teaspoon dried basil
  • ¼ teaspoon dried oregano
  • 2 teaspoons olive oil for drizzling on tian
  • 1 cup (4 ounces) shredded Gruyère cheese (See Tip 3)


  • Heat 2 tablespoons olive oil in a large skillet over medium heat. Add onions, ¾ teaspoon of salt, ¼ teaspoon of dried thyme, and ¼ teaspoon of black pepper. Cover the pan with a paper towel and then the lid. Cook over medium heat for 10 minutes. Remove the paper towel and cover. Continue cooking over medium heat for an additional 10 minutes until lightly caramelized. Add the garlic and cook for 30 seconds or until the garlic is fragrant. Transfer to 2 ½-quart casserole dish that has been sprayed with non-stick spray. (See Tip 4)
  • Bring a large saucepan of water with 1 tablespoon of salt to a boil. Add potatoes; cook for 8 to 9 minutes. Drain potatoes. Place a single layer on a paper towel-lined baking sheet. Blot dry with paper towels.
  • Place zucchini and tomatoes in a single layer on a paper towel-lined baking sheets. Sprinkle each with 1 teaspoon of Kosher salt. Let sit 30 minutes. After 30 minutes, blot dry with additional paper towels.
  • Layer potato, zucchini, and tomato alternately on top of the onions fitting the layers upright. Cover the onions completely. Drizzle with 2 teaspoons of olive oil. Sprinkle with ¼ teaspoon each of dried thyme, dried basil, and dried oregano. Cover with aluminum foil. May be prepared in advance up to this point and refrigerated.
  • Preheat oven to 375°F. Bake vegetable tian covered for 40 minutes. Remove from oven; remove aluminum foil. Sprinkle with cheese. Return uncovered to 375°F oven for an additional 30 minutes. (See Tip 5)
  • Yield: 6 servings. (See Tip 6)


  1. The casserole dish I used was oval and 11 ½ inches by 8 inches. For this size casserole dish that I used, I needed 36 slices each of potatoes, zucchini and tomatoes.
  2. Kosher salt serves several purposes here. First, when added to the water that the potatoes are boiled in, it flavors the potatoes. Second, it seasons the onions as they are cooking. Finally, when sprinkled on the zucchini and tomatoes, it serves to draw out excess moisture and also flavor the zucchini and tomatoes. This is important to prevent the tian from being soupy. In the end, all of the vegetables are perfectly seasoned.
  3. You could also use Monterey Jack, Parmesan, or Mozzarella cheese instead of Gruyère cheese.
  4. The reason that I place paper towels on the skillet before putting the lid on is to trap condensation that rises as the onions are cooking. This helps to remove excess moisture from the onions as they cook.
  5. If you are going to bake the tian as soon as it has been assembled, you can reduce the cooking time from 40 minutes to 35 minutes.
  6. Leftovers, if any, are amazing. I like to reheat them covered in the microwave for several minutes until heated through.


Calories: 255kcal | Carbohydrates: 31g | Protein: 9g | Fat: 12g | Saturated Fat: 4g | Cholesterol: 17mg | Sodium: 2280mg | Potassium: 837mg | Fiber: 5g | Sugar: 8g | Vitamin A: 774IU | Vitamin C: 44mg | Calcium: 192mg | Iron: 2mg