The words “onion” and “tart” don't seem like they should go together, do they? At least that’s what I thought before I tasted my first tarte d'oignon in France. But once I tried it, there was no doubt that this would become one of my favorite dishes.
As with other tarts, there are many recipes for savory onion tarts, but they are all variations on the same theme: softened or caramelized onions held together with eggs, cream, or cheese—or sometimes all three—and baked in flaky pastry dough. My preference is simply to add a bit of Gruyère to bind the onions; mixing the onion with egg and cream results in something more like a quiche, and adding only cream or crème fraiche makes the crust too soft.
You can use a tart tin for this recipe, or make a galette; both work well. If you’re using a tart pan, roll out the dough, press it into the pan, and refrigerate until you’re ready to use. If you roll out dough for a galette, put it on a piece of parchment on a baking sheet and keep it in the fridge until ready to use.
Though it is not from my Gourmet cookbook, this tart uses only five ingredients, six if you count the pâte brisé:
3-5 onions, depending on size
Gruyère, about 1 cup loosely packed
Melt enough butter in a pan to sauté all those onions, and just enough olive oil to keep the butter from browning. The trick for this tart is slice the onions thin and cook them s-l-o-w-l-y in a heavy bottom pan on the stove, about 40 minutes. Except for the occasional stir, they don’t need to be watched too carefully. The extra time you take cooking the onions results in soft, sweet, buttery, translucent onions that will fragrance your kitchen and caramelize to perfection. Once the onions are cooked, add just a teaspoon of balsamic vinegar, stir, and cook about 10 more minutes, until the onions are caramelized.
Take the dough from the fridge, spoon most of the Gruyère into the bottom of the pan (or on top of the rolled dough) then spoon the onions on top of the cheese. Sprinkle the top with the remaining cheese and bake in a 400 degree oven until the edges are brown.
Onions are probably our least expensive and most plentiful vegetable, yet we seldom consider them for a main dish. Perhaps this recipe will change that, oui?