I am always amazed at how a little heat and fat can transform a powerful, hot onion into melting sweetness. This custardy (and sweet) onion tart was dinner last night, along with a roasted beet and garden lettuce salad.
The Onion Tart is a Deborah Madison recipe via The New York Times. I made two small changes to the original version. I sautéed the onions in extra-virgin olive oil instead of butter, and I prebaked the tart crust for 15 minutes before filling with the onion mixture. (I never pour custard into an unbaked tart shell.)
Delicious directly from the oven, or at room temperature -- think lazy, French Rosé lunch!
for the filling:
• 2 slices of bacon, cut into 1/4-inch-wide pieces
• 1 1/2 pound onions, preferably white, diced
• 3 tablespoons extra-virgin olive oil
• 1 generous teaspoon fresh thyme leaves
• Sea salt
• Freshly ground black pepper
• 3 large eggs
• 1/2 cup crème fraîche or heavy cream
• 1/2 cup whole milk
• 1 cup grated Gruyére cheese
for the crust:
• 1 cup plus 2 tablespoons white whole-wheat flour
• 1/4 teaspoon salt
• 6 tablespoons cold, unsalted butter cut into small cubes
• 3 tablespoons ice water
1. To make the crust: Place the flour and salt in the bowl of a food processor. Pulse once or twice to combine. Add the cold butter and pulse until the size of small peas. Add the ice water slowly, while pulsing. Gather the dough and place on a piece of plastic wrap. Press into a disc and wrap securely. Refrigerate for 2 hours.
2. Fry the bacon in a skillet until brown. Remove bacon to paper towels to drain; wipe the skillet dry. Over medium-low heat, add the olive oil to the skillet and then the onions. Sprinkle fresh thyme leaves over the onions. Cook, stirring frequently, until onions just begin to turn golden, about 20 minutes. Lower the heat if they start to brown. You want a pale, gold color when finished. Season with salt and pepper. Remove onions from heat and let cool.
3. Remove the tart dough from the refrigerator. On a lightly-floured work surface, roll the dough to fit either a 9-inch round, or a rectangular tart pan. Transfer the dough to the pan and gently press into place. Trim dough at edge of pan. This is a very delicate dough and you will most likely have rips and tears. Use the trimmed dough to patch tears. Save any remaining scrap dough at room temperature while tart shell bakes. Place tart shell in freezer while preheating oven. Preheat to 400˚F. When ready, take the tart shell from the freezer and line with foil. Fill the shell with dried beans or rice and bake on the middle shelf of oven for 15 minutes. Carefully remove foil and filling and place tart pan on a rimmed baking sheet. Carefully patch any additional holes in the crust with reserved, room temperature dough. Set aside until needed.
4. In a large mixing bowl, whisk together the eggs, crème fraîche (or heavy cream), milk, and Gruyére cheese. Add the onions and reserved bacon; mix gently. Ladle the onion-custard mixture into the tart shell and place the baking sheet on center shelf of oven.
5. Bake tart for 45 - 50 minutes or until custard is set and golden. Let cool briefly before cutting. Serve with a garden salad.
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