Preheat the oven to 350 degrees Fahrenheit and line a 8” x 8” cake pan with parchment paper.

Add the softened butter and sugar to the bowl of a stand mixer fitted with a paddle attachment. Cream butter and sugar on medium-high speed until the butter sugar mixture is fluffy. Note: if you don't own a stand mixer, use a large bowl and an electric hand mixer.

Use a rubber spatula to scrape the sides of the bowl, add the egg and vanilla extract, and beat until the wet ingredients are well combined.

In a separate bowl, stir together the gluten-free all-purpose flour, baking powder, cinnamon, and sea salt (dry ingredients).

Leaving the mixer on medium-low speed, slowly pour the flour mixture into the mixer with the wet ingredients. Mix just until combined.

Transfer the cowboy cookie dough to the prepared baking dish and use a rubber spatula to press dough into an even layer. If you’d like, sprinkle the top of the dough with extra chocolate chips, shredded coconut, flaky sea salt, and/or chopped pecans.

Bake on the center rack of the preheated oven for 20 to 30 minutes, or until golden-brown around the edges. I bake mine for 22 minutes, which results in a crispy edge and a very gooey center. For chewy, underdone cookie bars, bake for 20-22 minutes, or until the internal temperature is 168 to 178 degrees F. For cookie bars with a golden brown crisp that have set up but are still gooey, 22 to 25 minutes. Harder, crispier cookie bars, 28 to 30 minutes.

Allow cookie bars to cool for at least 20 minutes before slicing. The longer you wait to slice the bars, the cleaner the slices will come out.

To slice bars easily, Pull on the edges of the parchment paper and lift the full batch out of the baking dish and transfer it to a cutting board. Be sure to use a sharp knife to cut the bars in order to get clean slices.