At Coco this summer, these tarts got a final garnish of quartered Sun Gold cherry tomatoes; arugula dressed lightly with lemon juice, olive oil, and salt; and small cubes of feta cheese.
Puff pastry (adapted from the Zuni Café Cookbook):
6½ ounces (1½ cups) all-purpose flour
6 ounces (1 ½ sticks) cold butter, sliced into ¼-inch-thick squares
9 tablespoons iced water
Place flour in a mound on a cool work surface. One at a time, toss butter chips in the flour and press flat with your fingers, being careful not to overwork or let them melt. Slowly pour ice water into the flour mixture and stir lightly with your fingers until the water is just incorporated. Using a bench scraper, fold the mixture over onto itself a few times, just until there are no more major wet/dry spots. (It will be a shaggy mess. This is not only OK, but preferable.) Wrap in plastic wrap and let rest in the refrigerator for 30 minutes.
Dust the work surface with a couple tablespoons of flour, and roll the dough into a long rectangle, dusting the dough and rolling pin with as little flour as possible to keep it from sticking. Fold the dough in thirds back onto itself, and repeat the rolling and folding process. Wrap in plastic and refrigerate another 30 minutes. Repeat the rolling and folding process (roll and fold, roll and fold) again, then wrap tightly in plastic and refrigerate at least 1 hour, preferably overnight.
Cut dough into 12 pieces and roll each out into a roughly 6- by 4-inch rectangle, docking each with a fork to prevent the dough from bubbling while cooking. Place on baking sheets, wrap in plastic, and refrigerate until cold, 1 hour.
Caramelized onion topping
2 large yellow onions, peeled, halved, and thinly sliced
3 tablespoons olive oil
¼ cup thyme, chopped
18 Kalamata olives, pitted and quartered
In large sauté pan, heat oil over medium-low heat. Sauté onions, working in batches if necessary to prevent overcrowding, until onions are lightly browned, 10–12 minutes. Cool to room temperature, then stir in thyme.
Preheat oven to 400°. Lightly brush each crust with olive oil, then top with onion mixture and 6 olive quarters, and lightly salt to taste. Bake until edges and bottoms of tarts are golden, 30–40 minutes.