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Potato Gratins
Recipe
2 hr 45 min

Potato-Tomato Gratin

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Potato-Tomato Gratin
Author: Cristin Walsh

Recipe By Cristin Walsh

Published on August 27, 2026

For a sweeter, cleaner, lighter potato gratin, ditch the heavy cream and add tomatoes.

Time

2 hr 45 min

Yield

Serves 6 to 8

Why This Recipe Works

Fresh tomatoes add great flavor to potato gratin, but they also add lots of moisture. For a clean flavor profile, we nixed the cream for this Provence-inspired dish. Broth was a better fit, but as it turned out, the juice from the tomatoes alone provided enough moisture to cook the potatoes to tenderness. Caramelized onions, kalamata olives, and fresh thyme add even more Mediterranean flavor to this gratin, and a topping of nutty Gruyère cheese is the finishing touch.

Ingredients

2 tablespoons olive oil
2 onions, halved and sliced thin
Salt and pepper
2 garlic cloves, minced
¼ cup water
½ cup pitted kalamata olives, chopped
3 pounds plum tomatoes, cored and sliced ¼ inch thick
2 pounds russet potatoes, peeled and sliced ⅛ inch thick
2 teaspoons minced fresh thyme
8 ounces Gruyère cheese, shredded (2 cups)

Instructions

Cook along with these step-by-step instructions

step 1 imagestep 2 imagestep 3 imagestep 4 image
  1. Adjust oven rack to upper-middle position and heat oven to 400 degrees. Grease 13 by 9-inch baking dish. Heat oil in 12-inch skillet over medium heat until shimmering. Add onions, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring frequently, until soft and golden brown, 15 to 20 minutes.
    Recipe Tip
    True caramelized onions can take nearly an hour and boast a deep mahogany flavor, but for the purposes of this dish you’re just looking for a soft texture and golden color.
  2. Add garlic and cook until fragrant, about 30 seconds. Add water and cook until nearly evaporated, scraping up any browned bits, about 2 minutes. Off heat, stir in olives; set aside.
  3. Shingle half of tomatoes in even layer in prepared dish. ­Shingle half of potatoes over tomatoes and sprinkle 1 teaspoon thyme, 1/2 teaspoon salt, and 1/4 teaspoon pepper over top. Spread onion mixture evenly over potatoes. Shingle remaining potatoes over onions. Shingle remaining tomatoes over potatoes. Sprinkle remaining 1 teaspoon thyme, 1/2 teaspoon salt, and 1/4 teaspoon pepper over top.
    Recipe Tip
    Shingling just means you’re arranging the rounds in an even layer and each slice is slightly overlapping the one before it. If there are any smaller pieces of potato or misshapen slices use them for the bottom layer where they won’t be visible.
  4. Bake, uncovered, for 1 hour. Sprinkle with Gruyère and continue to bake until cheese is browned and bubbly and potatoes are completely tender, 25 to 30 minutes longer. Let cool for 30 minutes. Serve.
    Recipe Tip
    The water inherent in tomatoes provides enough moisture to cook the potatoes while this dish is baking. At the same time, the heat from the oven cooks off the excess moisture so the dish emerges perfectly cooked with just the right amount of sauce, but it needs to be uncovered the whole time for this to occur.

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Potato-Tomato Gratin

Recipe By Cristin Walsh

Published on August 27, 2026

Time

2 hr 45 min

Yield

Serves 6 to 8

Potato-Tomato Gratin

Ingredients

2 tablespoons olive oil2 onions, halved and sliced thinSalt and pepper2 garlic cloves, minced¼ cup water½ cup pitted kalamata olives, chopped3 pounds plum tomatoes, cored and sliced ¼ inch thick2 pounds russet potatoes, peeled and sliced ⅛ inch thick2 teaspoons minced fresh thyme8 ounces Gruyère cheese, shredded (2 cups)

Instructions

  1. Adjust oven rack to upper-middle position and heat oven to 400 degrees. Grease 13 by 9-inch baking dish. Heat oil in 12-inch skillet over medium heat until shimmering. Add onions, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook, stirring frequently, until soft and golden brown, 15 to 20 minutes.
    Recipe Tip
    True caramelized onions can take nearly an hour and boast a deep mahogany flavor, but for the purposes of this dish you’re just looking for a soft texture and golden color.
  2. Add garlic and cook until fragrant, about 30 seconds. Add water and cook until nearly evaporated, scraping up any browned bits, about 2 minutes. Off heat, stir in olives; set aside.
  3. Shingle half of tomatoes in even layer in prepared dish. ­Shingle half of potatoes over tomatoes and sprinkle 1 teaspoon thyme, 1/2 teaspoon salt, and 1/4 teaspoon pepper over top. Spread onion mixture evenly over potatoes. Shingle remaining potatoes over onions. Shingle remaining tomatoes over potatoes. Sprinkle remaining 1 teaspoon thyme, 1/2 teaspoon salt, and 1/4 teaspoon pepper over top.
    Recipe Tip
    Shingling just means you’re arranging the rounds in an even layer and each slice is slightly overlapping the one before it. If there are any smaller pieces of potato or misshapen slices use them for the bottom layer where they won’t be visible.
  4. Bake, uncovered, for 1 hour. Sprinkle with Gruyère and continue to bake until cheese is browned and bubbly and potatoes are completely tender, 25 to 30 minutes longer. Let cool for 30 minutes. Serve.
    Recipe Tip
    The water inherent in tomatoes provides enough moisture to cook the potatoes while this dish is baking. At the same time, the heat from the oven cooks off the excess moisture so the dish emerges perfectly cooked with just the right amount of sauce, but it needs to be uncovered the whole time for this to occur.
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