Preheat the oven to 350°F and line a large baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking soda, baking powder, salt, pumpkin pie spice, and cinnamon.
In a large bowl, using a rubber spatula, mix the brown sugar and cooled brown butter. It's ok if they are not completely mixed together.
Mix in the egg yolk, maple syrup, vanilla, and pumpkin until incorporated. Again, it's ok if it's not completely mixed together. The dough will come together.
Add the dry ingredients and fold into the batter until completed incorporated, making sure to not over mix the dough. The dough will be soft, but it will firm up a little as you make the coating.
In a small bowl, mix the brown sugar, granulated sugar, and cinnamon for the coating.
Using a cookie scoop or tablespoon, scoop out the dough and roll in the cinnamon sugar mixture. (See notes.)
Place the cookie dough balls onto the prepared baking sheet, making sure to space them about an inch apart so they have room to spread.
Bake for 8-10 minutes or until the edges are cooked but the middle looks like it's slightly under done. You don't want to over bake the cookies, otherwise they may not be chewy. (See notes.)
Sprinkle with flaky sea salt if using and allow the cookies to rest on the baking sheet for a couple minutes. Then transfer to a cooling rack to cool completely. Repeat until you have used all of your cookie dough.