Every time I have caramelized onions, I wonder why caramelization isn’t obligatory for all onions. It is just magical how onions can transform from sharp and pungent to sweet and magnificent with just a little heat and a little patience. This tart is lovely because it lets the onions shine. If you can crank out a decent pie crust, all the better. Flaky dough + creamy onions = heaven.
You could also consider this tart a perfect opportunity to eat bacon. I’d cook the bacon first, drain off some of the fat from the pan, add a tablespoon of butter and then saute the onions in the bacon fat and butter combo. Chop up the bacon in to bits and then combine them with the onion custard before you pour it into the tart shell.
We had this tart for dinner with a salad and roasted veggies. It would also go nicely with soup or roast chicken. I had it for lunch the next day and can attest that it reheats like a dream—in the unlikely event that you have leftovers.
Simple Caramelized Onion Tart, adapted from Orangette
1/2 recipe for flaky pie dough
3 tablespoons butter
2 large yellow onions, peeled and sliced thin
1/2 cup heavy cream
pinch of nutmeg
Flaky Pie Crust
2 1/2 cups all purpose flour
1 1/4 teaspoons kosher salt
2 1/2 sticks unsalted butter
about 5 tablespoons ice water
Make the pie crust the night before. In a food processor, combine flour and salt. Remove the butter from the fridge and cut into 1 inch cubes. Add them to the flour mixture. Process until the butter chunks are about the size of peas. Add the water and pulse a few times to combine. Divide into two equal balls, wrap in plastic wrap and refrigerate.
Preheat your oven to 375 degrees.
In a heavy-bottomed pan over medium low heat, melt two tablespoons of butter. Add the onions. Caramelize the onions stirring occasionally. Depending on your stove, this will take somewhere in the neighborhood of 45 minutes.
While your onions are caramelizing, roll out the pie dough. Put it in a 9-inch tart pan and trim off the excess. My favorite Julia Child trick for getting perfect edges on a tart is to drape the excess dough over the edges of the pan and then roll the rolling pin on top of the dough over the edges of pan. The sharp edges of the pan will cut through the dough and you can easily pull away the excess. Put the tart shell in the fridge until your onions are done caramelizing.
Whisk together the egg, cream, salt, pepper and nutmeg.
After the onions are a medium brown, remove them from the heat. Mix them with the egg mixture and pour into the tart pan. Bake for 30 – 45 minutes, until the top of the tart is golden brown. Unmold the tart and serve hot or let cool to room temperature and serve.