Remove the puff pastry from the package and let thaw at room temperature for about 30 minutes, or until no longer frozen but still cool.
Meanwhile, heat the oil in a large skillet over medium heat. Add the onion and garlic, and cook 5 minutes, or until the onion is slightly tender. Stir in the zucchini and saute just until it begins to soften, about 5 minutes. Mix in the drained tomatoes and raise the heat to medium-high. Cook, stirring often, until the zucchini is tender but not mushy and the juices have evaporated. Let cool.
Lightly butter a dark-colored 9-inch tart pan with a removable rim or a glass pie plate. On a lightly floured surface, roll the puff pastry into an 11-inch square. Fit it into the tart pan or pie plate. Trim off the overhanging pieces of pastry with scissors. Refrigerate the crust, uncovered, for 15 minutes, or up to 8 hours, covered.
Preheat the oven to 425 degrees F.
Beat the eggs in a large bowl. Stir in the cheese, salt, pepper, and cooled vegetables. Spoon the mixture into the tart pan. Bake 25 to 30 minutes, or until the pastry is brown and a knife inserted in the center of the tart comes out clean. Remove the outer rim of the tart pan. Let the tart cool on a wire rack for 20 minutes before slicing. It is best to serve this tart very warm rather than piping hot.
Recipe courtesy of Jeanne Lemlin