Onion Tart

There is a long list of variations of savory galettes and most of them begin with sautéed onions. Sautéed onions are the perfect foil for the crisp, buttery crust of a tart. When combined with other vegetables, onions add protective moisture and deep flavor as the tart bakes in the oven. The pastry can also be rolled into long thin rectangular tarts, which can be cut into small pieces that make very popular finger food for a party. Surprisingly, onions vary quite a bit, and not just in appearance. Sometimes they cook quickly and are so juicy they need to be drained before they can be used; other times they take a long time to soften and don’t give off any liquid to speak of. Onions with very thin skins are usually much more sweet and juicy, while those with very hard, dark, golden skins tend to take longer to cook. All onions will eventually soften and be delicious, but when given the choice, I recommend selecting large onions that have a delicate, thin, lighter skin. In the summer, when they are in season, sweet Walla Walla, Vidalia, or Bermuda onions make excellent tarts, baking up almost as sweet as honey. In the spring there are fresh onions, or spring onions, that have not been dried and cured, and still have their green stalks attached. Peel them and trim off their stalks, slice them thick, and cook until just soft. The flavor of spring onions is delicate and less sweet than that of mature cured onions. The right amount of onions cooked to the right consistency is what makes a good tart. Pile the onions into a low-sided, heavy-bottomed pan with a generous amount of fat, and cook them slowly with herbs until soft and tasty; this will take at least 30 minutes. The onions must be cooled before they are spread onto the pastry or they will melt the butter before the tart bakes. The onions should be moist but not dripping wet or the tart will be soggy. If the onions are too juicy, drain them. Save the juice; it can be reduced and served with the tart as a little sauce or added to a vinaigrette. If the onions are still juicy, even after draining, sprinkle a little flour over the pastry (avoiding the border), before adding the onions, to soak up some of the juice while the tart cooks. Bake on the lowest rack of the oven for a crust that is crisp and golden brown on the bottom. Check the underside by gently lifting up the tart with a spatula. When the tart is fully baked, slide it off the pan onto a cooling rack to rest. If left on the baking pan to cool, it will steam and the pastry will not stay crisp. Once you have mastered a basic onion tart, there are many variations you can try: add sliced sweet or hot peppers to the sautéing onions about halfway through cooking; grate some summer squash and stir it into the onions during their last few minutes of sautéing; or, before you fill the tart, while the onions are cooling, stir in either seasoned cherry tomato halves or roasted, peeled, and sliced peppers. You can also top the layer of onions with sliced tomatoes or lightly grilled slices of eggplant. For a sweet and savory tart, mix chopped roasted figs into the onions. Other variations include sprinkling the pastry with grated cheese or brushing it with a slurry of chopped herbs and olive oil before spreading on the onions. Artichoke hearts also can either be sautéed and stirred into the onions, or sliced and baked and arranged on top of them; when the tart comes out of the oven, try painting it with garlic and herb butter. And most of the year you can mix the onions with sautéed greens—collards, chard, spinach, broccoli rabe, or mustard. Or when the tart has only 10 minutes left to bake, top it with anchovies and black olives.