When you're knee-deep in holiday cooking and baking, it can feel like you never turn your oven off. So the most helpful recipes are ones we can prepare ahead of time, and our cheese and onion tart recipe fits the bill.

This dish is assembled much like a quiche, so the components should look familiar. The tart dough can be made weeks ahead and frozen - you can even roll it and freeze it in the pan, so you don't have to clean up stray flour the week of your party. The filling is a simple egg custard, layered with caramelized onions.You can caramelize the onions earlier in the week, and even mix in and cook the flour that's added as a thickener. Just cool the whole mixture and seal it tightly in a zip-top bag. Bring it to room temperature, then spread it in your tart shell when you're ready.You can bake the assembled tart a day or two before your party. You won't want to serve it fresh out of the oven anyway, since the custard filling needs to cool and set. Remove it from the refrigerator the day of your party and either serve it at room temperature or quickly warm it in the oven before slicing.If you decide to experiment with cheese, remember that you will want one that melts well, like cheddar, fontina, or young Gouda. A smoked Gouda will bring out the flavors of the bacon and contrast nicely with the sweet onions.You can also serve this tart as small bites. Use a square or rectangular tart pan to make your tart, and once it is baked and cooled, cut it into small squares that can be passed as hors d'oeuvre. You can garnish each piece with a parsley leaf or a dollop of apple butter, if you like. And if you have any leftovers (you probably won't), this tart makes a great next-day breakfast or lunch item. Serve it alongside some fresh fruit or a light salad.Cheese and Onion TartMakes one 10-inch tartServings: 10Start to finish: 3 hours, 15 minutesTart Dough:2 2/3 cups all-purpose flour1/8 teaspoon salt7 tablespoons unsalted butter, cubed and chilled7 tablespoons ice waterFilling:1 quart water3 thick slices bacon¼cup unsalted butter5 cups finely sliced onionsSalt, to tasteFreshly ground black pepper, to tasteFreshly grated nutmeg, to taste2 tablespoons all-purpose flour1 cup Gruyère, diced½cup heavy cream½cup whole milk1 large egg, lightly beatenPreheat the oven to 400 degrees F.To make the dough: Place the flour and salt in a mixing bowl and work the cold butter into the flour until the mixture resembles fine crumbs. Add the cold water and mix just until the dough forms a ball; do not knead or overwork the dough. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.On a board or work surface lightly dusted with flour, roll out the dough into a 12-inch circle with a thickness of 1/8 inch. Line a 10-inch tart pan with the dough and chill the tart shell for at least 30 minutes in the refrigerator.Prick the bottom and sides of the tart shell with the tines of a fork and then line with parchment paper or aluminum foil. Weigh down the paper with some dried beans, lentils, or rice to keep the dough from puffing up as it bakes.Blind bake the tart shell until the dough sets and the edges look dry, 10 to 12 minutes. Remove the paper or foil and the beans and set the shell aside to cool. Reduce the oven temperature to 350 degrees F.To make the filling: Bring the water to a boil in a pot over high heat. Add the bacon slices and blanch for about 10 seconds. Remove the bacon from the water and allow to drain completely. When cool, cut into 1/4-inch dice.In a saute pan over low to medium heat, melt the butter. Add the onions and season with salt, pepper, and nutmeg. Cook until the onions are a rich golden brown and smell sweet, about 50 minutes. Do not hurry this process; the onions should cook slowly to attain a rich golden color.Sprinkle the flour onto the onions and cook for another 5 to 7 minutes, stirring to avoid burning the onions. Remove from the heat and allow the mixture to cool.To fill the tart: Place the onion mixture and cheese on the bottom of the prebaked and cooled tart shell. In a bowl, whisk together the cream, milk, and egg. Pour the milk mixture into the tart shell. Sprinkle the pieces of blanched bacon on top.Place the tart on a sheet pan on the lowest shelf of the oven and bake until the crust is golden brown and the filling is completely set, about 25 minutes.Chef's note: To facilitate removing the finished tart from the pan, line the bottom of the tart pan with parchment paper and grease with butter before lining with the dough.Nutrition information per serving: 378 calories; 207 calories from fat; 23 g fat (14 g saturated; 1 g trans fats); 87 mg cholesterol; 175 mg sodium; 33 g carbohydrate; 2 g fiber; 3 g sugar; 10 g protein.