Impress friends with this delicious tart that requires minimal effort, but tastes like you spent forever in the kitchen. The most difficult part of the process is caramelizing the onions, but it's also the key for its success. Once that's done, everything else comes together in minutes for the bake.
And while you could try regular walnuts for this recipe, this is one of those dishes where our walnuts really shine because there's no bitterness or skin.
Directions
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Preheat your oven to 400°F. Then thinly slice the onions.
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Heat olive oil in a large pan over medium heat. Add the sliced onions, sugar, salt, and pepper. Cook, stirring occasionally, until onions are deeply caramelized, about 30-40 minutes. Remove from heat and let cool slightly.
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While your onions are cooling, shred the Gruyere cheese and chop walnuts. Then whisk together the eggs, heavy cream, and half the thyme in a bowl.
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Press the puff pastry into a 9-inch tart pan, trim off any excess. Prick the bottom with a fork. Spread the shredded Gruyere cheese onto the bottom of the tart shell and sprinkle the walnuts on top. Then pour the egg mixture and top with the caramelized onions. Bake the tart for 25-30 minutes, or until the filling is set and the top is golden brown.
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Sprinkle the remaining thyme on top and let it cool for a few minutes before serving.
