Tomato Tart with Goat Cheese and Caramelized Onion

Ingredients

• 1¼ cups all-purpose flour, plus more for dusting and rolling out
• ¼ teaspoon salt
• 8 tablespoons very cold butter, (1 stick), cut into ¼ “ small pieces
• 2 to 4 tablespoons ice water
• large Spanish or yellow onions, sliced stem to root in ¼ inch thick
• 3 tablespoons butter
• 1 tablespoon good green olive oil
• 1 tablespoon brown sugar
• ½ teaspoon salt
• 1 tablespoon of water
• 1 egg, beaten with 1 teaspoon cold water
• ½ to ¾ cup soft goat cheese, room temperature
• 2½ teaspoon sea salt
• ½ teaspoon freshly ground black pepper
• 2 to 3 lbs heirloom tomatoes, sliced ½ inch thick, if using cherries, halve.
• 12 large and 24 small fresh basil leaves, whole
• 9 inch tart pan with removable rim