1) Preheat your oven to 350°F and lightly grease 2 9X9 square pans. Beat the butter and sugar until light and fluffy.
2) Blend in the orange zest and flavorings.
3) Add the egg yolks one at a time on low speed, blending well.
4) Whisk together the flour, xanthan gum, and salt, then stir into the butter/sugar mixture just until thoroughly combined.
5) Scrape the bowl well to be sure all the dry ingredients are thoroughly incorporated.
6) Divide the mixture evenly between two lightly greased 9" x 9" pans.
7) Bake the shortbreads in a preheated 350°F oven for 25 to 30 minutes, or until their edges are nicely browned.
8) Wait about 10 minutes, then turn the shortbreads out of the pan gently. Cut immediately into desired shapes while still warm.
Yield: 2 9X9 square pans.