To Make the Dough:

1. In a large bowl, whisk together the flour, sugar, and salt. Using a pastry cutter, cut the cold butter cubes into the flour mixture until the butter pieces are pea-size and coated entirely in flour.
2. In a small bowl, whisk together the almond extract and cold water. Knead the liquid one tablespoon at a time into the flour-butter mixture with your hands until a thick and cohesive dough just begins to form.
3. Form the dough into a flat disc. Cover the disc completely in plastic wrap, and chill for at least 45 minutes in the refrigerator.

To Assemble and Bake:

1. Preheat the oven to 375°F. Line a baking sheet with parchment paper or a silicone mat and set aside.
2. Remove the dough from the fridge and let it sit at room temperature for about 10 minutes.
3. Slice each plum into 8 pieces, discarding the pits, and transfer to a large bowl. Sprinkle the flour, sugar, lemon zest, and spices over the plums and gently toss together until the plums are evenly coated. Set aside.
4. Remove the dough from the plastic wrap and place on a lightly floured work surface. Dust the top of the dough with flour. Using a rolling pin, roll and flatten the dough into a circular shape about 12 inches in diameter and 1/8 inch thick. Carefully transfer the dough to the prepared baking sheet.
5. Arrange the plums in a pile in the center of the dough, leaving about 2 inches of space around the edges. Fold the edges toward the center, pleating them around the plum filling.
6. Whisk together the egg and 1 tablespoon cold water. Brush the crust with the egg wash and lightly sprinkle with turbinado sugar.
7. Immediately transfer the baking sheet to the oven. Bake for 40-45 minutes, rotating the baking sheet halfway through, until the fruit starts bubbling and the dough turns golden brown.
8. Remove from the oven. Cool the galette on the baking sheet for about 5 minutes. Serve while still warm, or transfer to a cooling rack to cool completely and serve at room temperature. Store any leftovers in an airtight container in the refrigerator or at room temperature for up to 3 days.