In a food processor, combine flour and salt. Add cold cubed butter and pulse until the mixture resembles coarse crumbs. Gradually add ice water, 1 tablespoon at a time, until the dough comes together.

1. Gather the dough into a ball, flatten into a disc, and wrap in plastic wrap. Refrigerate for at least 30 minutes.
2. In a large pan, heat olive oil over medium heat. Add the thinly sliced potatoes, cook for 5-7 minutes until they soften. Season with salt, pepper, and chopped thyme (or rosemary). Set aside to cool.
3. Preheat oven to 375°F (190°C). Roll the chilled dough on a floured surface into a 12-inch circle and transfer to a parchment-lined baking sheet.
4. Arrange the cooked potatoes in concentric circles on the dough, leaving a 1-2 inch border around the edges. Fold the dough edges over the potatoes to form a rustic border.
5. Bake in the preheated oven for 30-35 minutes, until the crust is golden and the potatoes are tender.
6. Once out of the oven, scatter arugula over the top and drizzle with crème fraîche. Garnish with lemon zest if desired. Serve warm or at room temperature.