Thinly slice zucchini into 1/16 inch thick round slices. Sprinkle with 1 tablespoon salt and place in colander. Let sit for at least 30 minutes and up to 1 hour.
Preheat oven to 400 degrees F.
Lightly flour a clean working counter with flour. Slightly roll out puff pastry so that it's big enough to cover a 9-inch pie dish. Transfer puff pastry to baking dish and gently press dough into dish to create a crust. Trim excess dough. Poke puff pastry with fork to prevent from puffing up. Bake for 12 minutes or until golden brown. Remove from oven and let cool completely.
Meanwhile, make olive tapenade feta filling. Pulse together olives, capers, garlic, lemon juice, and olive oil in a food processor until coarsely chopped. Transfer tapenade to a bowl and add Greek yogurt, egg, feta, salt, and pepper. Mix until well combined. Spread olive filling in an even layer on puff pastry.
Line baking sheet pan with paper towels and lay zucchini slices on top. Pat dry. Arrange zucchini slices on tart so that they're standing up, slightly overlapping the slices until the entire tart is covered. You may have extra zucchini slices.
Drizzle zucchini with 1 tablespoon olive oil and season with salt and pepper. Bake zucchini tart for 45 - 55 minutes or until zucchini is tender. Remove from oven and let cool slightly.
Slice zucchini tart and place dollop of creme fraiche on top. Drizzle with truffle oil if desired (but highly recommended!).
Notes
The puff pastry can be baked the day before. You can also prepare the olive tapenade the day before and fill the puff pastry with the tapenade on the day you are serving the zucchini tart.