As of 2015, Lidia Bastianich does not have a recipe available for onion tarts. However, she does have other tart recipes available on her website ranging from sweet to savory, such as a squash and ricotta tart.
Although Lidia Bastianich doesn't have an onion tart recipe, there are plenty available online, such as Emeril Lagasse's recipe available on FoodNetwork.com. Make these tarts by caramelizing 2 cups of thinly sliced onions in 2 tablespoons of butter over medium heat in a skillet. Season with salt and pepper, and saute for four minutes before adding 1 teaspoon of finely chopped garlic. After one minute, remove the skillet from the heat and allow the onions to cool. Mix the cooled onions and 1/4 pound of crumbled goat cheese in a bowl, and add salt and pepper.
Cut 2 1/2-inch circles from a sheet of puff pastry using a cookie cutter. Put the dough circles on a baking sheet lined with parchment. Prick each one with a fork, and brush with a beaten egg. Spoon the onions onto the pastry circles, leaving a border of dough. Bake them for 15 minutes at 375 degrees Fahrenheit. Remove the tarts from the oven, and garnish with 1 tablespoon of chopped fresh parsley before serving.