Strawberry Rhubarb Crostata

1 1/4 cups whole wheat pastry flour + more for dusting
1/4 teaspoon sea salt
1 stick cold butter, cubed
4-6 tablespoons ice water
2 heaping cups sliced or quartered strawberries (cut up depending on how big they are)
2 heaping cups rhubarb, ½ inch dice
1 teaspoon vanilla
1/2 cup cane sugar
2 tablespoons arrowroot (cornstarch is ok too)
Big pinch cinnamon
Pinch salt
1 egg, beaten
1-2 tablespoons turbinado sugar

1. In a food processor (or do it by hand using a pastry cutter), pulse 1 1/4 cups of flour and salt. Pulse in the butter cubes until they are about the size of peas.
2. Add 4 tablespoons ice water and pulse a few times until the dough just starts to come together. The dough should stick together when you pinch it. If it’s still crumbly, add another tablespoon or two of water. Dump the mix onto a large piece of plastic wrap spread out on the counter. Gather up the wrap around the dough and form dough into a smooth, thick disc. Refrigerate for 30 minutes.
3. While the dough is chilling, cut up the strawberries and rhubarb. Add to a bowl along with the vanilla, sugar, arrowroot, cinnamon, and salt. Toss it all together until well mixed.
4. Heat oven to 400°F. On the countertop lightly dusted with flour, roll out dough to about a 12 inch circle and about 1/8 inch thick; carefully transfer dough onto a baking sheet lined with parchment paper.
5. Pour strawberry mixture into the center of the dough and spread it out leaving about 2 inches of dough around the edges.
6. Fold the dough over the mixture, gently pleating it as you go. Brush the dough with the beaten egg and sprinkle generously with turbinado sugar. Bake for 30-35 minutes until golden brown and bubbly. If some of the filling has leaked out during baking, no problem. The filling firms up as it cools. Let cool for at least 30 minutes before cutting and serving. Can be served warm or room temperature with whipped cream or vanilla ice cream.