In stand mixer, cream butter and sugars until fluffy.
Add eggs, orange zest, and vanilla extract, beat until everything is fully incorporated and smooth.
In a large bowl, mix together flours, starch, baking soda, spices, xanthan gum, and salt.
Slowly add this dry mix to the mixer bowl, and carefully mix until well incorporated and smooth. Add oats and butterscotch chips, continue mixing just until well incorporated.
Wrap dough in plastic film, chill for 1 hour.
Preheat oven to 350 F (180 C), line baking sheets with parchment paper.
Roll 1.5" balls out of the cookie dough. I like to use an ice cream scoop for ease and consistency in size.
Arrange dough balls on baking sheets. Leave at least 2" between cookies - they flatten out a fair amount.
Gently press the tops of each slightly - flatten JUST enough to prevent the dough from rolling.
Bake for 11-13 minutes. Cookies will look puffy, but flatten out as they cool. Do not over bake!
Allow cookies to cool for 2 minutes before removing from baking sheets.
Cool completely before storing in an airtight container