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+ servings

Heirloom Tomato and Basil Gratin


  • 2 lb heirloom tomatoes
  • 1 ¼ lb potatoes, washed and unpeeled
  • 6 cups thinly sliced onion (about 2 pounds)
  • ¼ cup olive oil, divided
  • ½ cup Greek yogurt
  • 1 Tbsp clarified butter
  • a small handful of basil leaves, slivered
  • sea salt and freshly ground pepper

  • Spice Blend
  • 1 ½ tsp whole cumin seeds
  • 2 ½ tsp curry powder
  • ½ -¾ tsp red pepper flakes


  • Prepare the Spice Blend
  • Combine the spices in a small bowl and set aside

  • Caramelize the Onions
  • In a large skillet, heat 2 Tbsp of olive oil over high heat. When hot, stir in the onions and a pinch of salt. Cook, stirring often until the onions soften (~4-5 minutes)
  • Turn the heat to medium and stir in the clarified butter. Stirring frequently, cook another 10 - 15 minutes, or until the onions are just beginning to caramelize.
  • Dial the heat back to medium-low, and continue cooking, until the onions are deeply golden (~ another 20 minutes)
  • A minute or two before the onions are finished cooking, stir in the spice blend.
  • Remove the pan from the heat and set aside

  • Assemble and Bake
  • Preheat the oven to 350° F
  • In the meantime, slice the potatoes into ⅛" thick rounds (using a mandolin, if you have one).
  • Place them into a medium bowl along with the Greek yogurt, 1 teaspoon of salt, and a bit of pepper. Toss well, and set aside.
  • Use a knife to cut the tomatoes into ¼" thick slices. Arrange across a large plate and sprinkle with another teaspoon of salt and some pepper.
  • Layer half the caramelized onions across the bottom of a 9 x 9" baking dish (I used a 10" round cast-iron pan)
  • Using half of the potatoes and half of the tomatoes, arrange them on top of the onion layer
  • Drizzle with a couple tablespoons of Greek yogurt from the potatoes and a tablespoon of olive oil. Season the layer with a pinch of salt and half the basil.
  • Scatter the remaining onions across the potatoes and tomatoes already in the pan.
  • Then arrange another layer of tomatoes and potatoes on top. (This will be the top of your gratin)
  • Pour the remaining Greek yogurt from the potatoes, and last tablespoon of olive oil across the top. Season with another pinch of salt and the remaining basil.
  • Gently press down on the vegetables
  • Cover tightly with aluminum foil and bake for 2 hours, or until the potatoes are tender throughout the dish. Increase the oven to 450° F, uncover the gratin, and cook another 30 minutes, or until the top has is golden