This tart wound up being so savory and delicious, with a beautiful flaky crust. In a long rectangular shape, it's a real showstopper too! The recipe worked especially well by using a combination of butter and olive oil to cook the onions and bacon, and was further improved by the use of fresh herbs. The filling made three cups' worth, which filled the tart perfectly, and became nice and golden in the oven. There was no shrinkage of the pastry and it became really nice and flaky. I loved the combination of the sweet onions, salty bacon, and herbs, and the tart was so stunning to look at that I would definitely make this again. —Jennifer Philipp
Prepare dough: Combine flour, salt, and butter in a food processor. Pulse until small balls form, then add water until dough comes together. Roll into a disk and cover with plastic wrap. Refrigerate for 30 minutes.
Prepare filling: Heat olive oil in a nonstick pan and gently sauté onions until translucent. Remove the onions and set aside. Next, sauté bacon until crisp. Combine onions, bacon, cream, egg, thyme, rosemary, and garlic powder.
Preheat oven to 375° F. Roll out the dough to 1/8-inch thickness and press into a 4- x 13-inch rectangular tart tin. Dock the dough with a fork. Spoon in the onion mixture and top with salt and pepper. Bake for 45 minutes or until lightly browned. Cool to room temperature and serve.