Rustic onion tart with caramelized red onions, Gruyere cheese and a buttery crust.
Is there nothing better than caramelized onions?
Yes, they do take some time to prepare, but they’re not difficult to cook and it’s so worth the effort.
You can either use a ready made frozen crust (the flat or folded kind) or make your own crust.
Rustic Onion Pie
ingredients
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1 Butter and Sour Cream Dough Recipe* or 1 packaged flat pie crust (Trader Joe’s has one in the frozen section)
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3 medium red and/or yellow onions (enough for 5 to 8 cups, sliced)
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2 tablespoons extra virgin olive oil
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1 tablespoon butter
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Salt
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1 teaspoon balsamic vinegar
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1/2 teaspoon fresh thyme, chopped or 1/4 teaspoon dried thyme
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3/4 cup (unwrapped) coarsely grated Swiss Gruyere cheese
- *Sour cream dough:
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1 1/4 cup (160 g) all-purpose flour
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1 teaspoon of salt
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5 ounces butter (1 1/4 sticks, 10 Tbsp, 137 g), diced
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1/4 cup sour cream
method
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To make dough:
If making a crust from scratch, prepare the batter and let it cool in the fridge while you cook the onions.
For the dough, whisk together the flour and salt in a large bowl. Using your hands or a pastry cutter, cut the butter into the flour until the mixture resembles a coarse flour.
Add the sour cream and work into the batter with a fork. Shape the dough into a ball and shape into a disc. Wrap it in plastic wrap and refrigerate for at least an hour.
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Prepare the onions:
Peel the onions and slice lengthwise from the stem to the root. (See How to Cut an Onion)
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Caramelize onions:
Heat olive oil and butter in a large, heavy-bottomed skillet over medium-high heat. Once the butter has melted, add the onions and sprinkle with a little salt.
Cook, stirring occasionally, until onions are soft and translucent, 10 minutes.
Reduce the heat to medium-low and cook for an additional 40 minutes, stirring occasionally, until the onions are well browned.
Add balsamic vinegar and cook another 10 minutes until onions are fully caramelized. Remove from stove.
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Roll out the dough:
Preheat oven to 450°F. Take the dough out of the fridge and let it rest for 5 minutes before rolling it out.
On a lightly floured surface, roll out the dough to a diameter of 13 inches. Place the crust pastry onto a parchment-lined baking sheet.
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Layer cheese and onions on the dough:
Place everything but a few tablespoons of cheese in the center of the batter. Spread out to within 1 1/2 inches of the edges. Add the caramelized onions and layer them on top of the cheese. Sprinkle with thyme.
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Fold the edges:
Fold the edges of the crust pastry over so that you can still see a small circle of onion in the middle of the cake. Scatter the remaining cheese over the cake.
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Bake:
Place in the oven on the middle rack. Bake at 450°F for 10 minutes. Reduce heat to 350°F and bake an additional 20-25 minutes until crust is golden brown.
Remove from the oven and let rest for 10 minutes before serving.
