To make the crust:

1. Preheat the oven to 350° Fahrenheit.
2. Combine all of the crust ingredients in a medium sized bowl and mix well with a fork until a crumbly dough forms.
3. Press firmly into a 8 by 8 baking pan, going about 1/2 inch up the sides. For best results line the pan with parchment paper or foil first, then you can simply lift out the completed lemon bars.
4. Bake for 10 minutes.
5. Remove and cool while you make the filling.

To make the filling:

1. Melt the butter in a small saucepan on low heat.
2. Remove from heat and whisk in sweetener, lime juice, and lime zest until dissolved.
3. Whisk in the egg yolks and return to the stove over low heat.
4. Cook over low heat, whisking continually until the curd starts to thicken.
5. Remove from the heat and strain into a small bowl.
6. Whisk in the the xanthan gum and gelatin until dissolved and smooth.
7. Pour the filling over the par-baked crust and spread out evenly to the edges of the pan.
8. Bake the bars at 350 degrees (F) for 15 minutes.
9. Remove from oven the and cool for 30 minutes.
10. Cut into sixteen 2 x 2 squares and garnish with optional toasted coconut and grated lime zest before serving.
11. Store in an airtight container in the refrigerator for up to one week, or in the freezer for up to 3 months.