Preheat the oven to 425°F
In a large mixing bowl, combine the flour, brown sugar, baking powder, salt, ground cinnamon (optional), and baking soda
Cut the 1/2 cup butter into small cubes, then cut it into the dry ingredients until the mixture resembles coarse crumbs
In a small bowl, combine the pumpkin and buttermilk
Stir the pumpkin mixture into the dry ingredients just until combined
Roll the dough out on a well-floured surface to 1-inch in thickness
Use a 2 ½-inch biscuit cutter to cut out 6 round biscuits
Discard the dough scraps or form into 2 more biscuits
Place the biscuits on a greased baking sheet about 1 inch apart
Bake for 19-22 minutes, or until golden brown
Melt the remaining 2 tablespoons of butter and brush over biscuits as soon as they’re removed from the oven
Serve warm