Make the shortbread: In a small bowl, combine the coconut sugar, coconut nectar, orange zest, orange juice, vanilla, and stevia.
Whisk to begin dissolving the sugar. Set aside.
In the bowl of a food processor, process the walnuts, brown rice flour, coconut flour, glutinous rice flour, xanthan gum, baking powder, and salt to a fine powder.
Pour the wet mixture in a ring over the dry ingredients and process again just until the mixture comes together in a moist dough.
Pat the dough evenly into the pan.
Using a sharp knife, score the top of the dough to create 25 squares, then poke holes across the top of each square with a fork.
Bake for 28-35 minutes, rotating the pan halfway through, until the edges are golden.
Cool completely in the pan.
Once cool, invert onto a cutting board, then flip again so that the scored side faces up.
Carefully cut through the scored lines to separate the cookies.
Make the glaze:
Mix the coconut sugar and orange juice in a small bowl and stir until the sugar dissolves.
Use a pastry brush to brush the tops of the cookies, or use a teaspoon and drizzle a little glaze over each cookie.