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Tomato and Olive Potato Gratin

  • Author: Tessa
  • Total Time: 1 hour 35 mins
  • Yield: 6 servings 1x


You can prepare and serve this dish out of a single cast iron skillet for a rustic look, using crusty bread to soak up the delicious sweet onion and tomato broth


  • 2 lb. small red, white, or purple potatoes, scrubbed
  • 2 lb. tomatoes (5 medium)
  • 2 t kosher salt
  • 3 1/2 T oil (plus more if not baking in a skillet)
  • 1 1/2 large red onions, quartered and sliced thin (4 C sliced)
  • 1/4 t dried thyme
  • 1/4 t fennel seed, cracked in a mortar and pestle if you have one
  • 1 1/4 t ground black pepper
  • 1/2 C kalamata olives, pitted and roughly chopped
  • 3 cloves garlic, sliced
  • 8 thyme sprigs
  • 1/4 of a whole lemon, sliced very thin (skin on)
  • 1 T whole capers, rinsed
  • Optional for serving: grated parmesan cheese, sour cream, crusty bread


  1. Bring a large pot of water to boil over high heat. Meanwhile, slice the unpeeled potatoes 3/8″ thick (just over 1/4″ – fairly thick) and pierce the skin of each tomato in a few places. When water boils, add a generous pinch of salt, let it return to a boil, then add potato slices (work in batches if they don’t all fit). Cook for 5 minutes, even if water doesn’t return to a boil. Use a slotted spoon to remove to a colander set over a dish towel, then rinse with cold water and set aside. Submerge whole tomatoes in the boiling water for 30 seconds, until the skin just wrinkles. Remove to a cutting board and peel immediately by hand–the skin should slip off easily.
  2. Preheat the oven to 400 degrees (F).
  3. Heat 2 tablespoons oil in a 10 to 12 inch cast iron or oven safe skillet over medium high. Add onions, dried thyme, fennel, and a dash of pepper. Stir often for about 6 minutes, until onions have just browned. Turn off heat and distribute onions in an even layer. If you don’t want to build the gratin in the skillet, transfer onions to a 2 qt. lightly oiled baking dish.
  4. Seed and chop 1 tomato and sprinkle over the onions. Halve, seed, and slice remaining tomatoes crosswise. Sprinkle olives, half the garlic, 4 thyme sprigs, and half the lemon slices over chopped tomatoes. Make a single layer of slightly overlapping potatoes and sprinkle with salt and pepper. Top potatoes with half the tomato slices, followed by the rest of the garlic, thyme, lemon, and more salt and pepper. Make another layer of potatoes, followed by seasoning and the remaining tomato slices. If there are more potatoes (I had some), arrange over the top and season.
  5. Top with capers and drizzle the whole dish with 1 1/2 tablespoons olive oil, then cover with foil and bake 25 minutes. Uncover and bake in the upper third of the oven another 30 minutes, or until the potatoes are completely tender (easily pierced with a paring knife). If desired, broil the uncovered dish for a few minutes to brown the top layer but watch that the capers don’t dry out. Top with parmesan cheese and/or a spoonful of sour cream to serve (if not making it vegan), and spoon the broth from the pan over each serving. Use bread to soak up any extra sweet onion and tomato broth!


Recipe adapted from The New Vegetarian Cooking for Everyone.

As written, without optional ingredients, the gratin is gluten-free and vegan.

  • Prep Time: 40 mins
  • Cook Time: 55 mins
  • Cuisine: Vegan