Spread the pumpkin puree onto a plate. Pat with paper towels to “dry” the pumpkin. This will take several minutes and several paper towels. Continue blotting until the pumpkin has a thick, dough-like consistency and the original ½ cup has reduced to about ¼ cup (45–53g).
For the pumpkin scones: In a large mixing bowl, whisk together the gluten-free flour, brown sugar, baking powder, salt, cinnamon, nutmeg, ginger and cloves.
Grate the frozen butter using a box grater. Add the butter to the flour mixture and combine with a pastry cutter, two forks or your fingers until the mixture resembles pea-sized crumbs.
In a separate bowl, whisk together the dried pumpkin puree, sour cream, egg yolk and vanilla.
Using a rubber spatula, stir the pumpkin-sour cream mixture into the flour mixture until no dry bits of flour remain.
Spread out a large piece of plastic wrap. Using wet hands, transfer the dough to the plastic wrap. Clean and wet your hands again, then pat the dough into a 6-inch round about 1 inch thick. Wrap the dough tightly in plastic wrap and refrigerate for 30 minutes. (Do not refrigerate longer than 30 minutes.) Then freeze for 15 minutes while the oven preheats.
Preheat the oven to 500°F. Line a large baking sheet with parchment paper or a silicone baking mat.
After 15 minutes, remove the dough from the freezer. Spray a sharp knife with cooking spray and cut the dough into 6 equal wedges. Arrange the scones on the prepared baking sheet.
Place the scones in the oven, then immediately lower the oven temperature to 425°F. Bake for 12–14 minutes, until golden brown.
Remove from the oven. Transfer the scones to a wire rack and let cool for 20 minutes.
For the brown sugar glaze: Combine the brown sugar, milk, butter and salt in a medium saucepan over medium heat. Stir until the butter has melted and the mixture is smooth. Bring to a simmer.
Simmer for 1 minute, then remove from the heat. Whisk in the vanilla, sifted powdered sugar and cinnamon until smooth. Using a large spoon, drizzle the glaze evenly over the scones.