Preheat the oven to 350 degrees Fahrenheit. Line a sheet pan (or two) with parchment paper or a silicone baking mat. In a medium bowl combine the flour, oats, baking soda, kosher salt, and cinnamon. Stir and set aside.
In the bowl of a stand mixer cream the butter and both sugars together on medium speed until lighter and fluffy - about 3 minutes.
Add the egg and beat until combined. Scrape the sides of the bowl with a spatula to make sure everything is mixed well.
Add the flour mixture and beat until a cookie dough forms. Add the butterscotch chips and mix a few more seconds until they're dispersed evenly throughout the dough.
Using a small cookie scoop scoop 6 cookies onto the sheet pan and bake for 11 to 12 minutes. The edges should be slightly brown and the insides should look underdone.
Once cooled for a few minutes transfer the cookies to a plate or cooling rack.