- Preheat oven to 350°F.
- Whisk together the coconut flour, tapioca starch, baking powder, and salt.
- Use a stand mixer or hand mixer to combine the melted coconut oil, maple syrup, and vanilla extract. Slowly mix the dry ingredients into the wet ingredients. The mixture will become somewhat dry and clump up. This is expected.
- Grease an 8X8 glass baking dish with a little coconut oil then firmly and evenly press the shortbread mixture into the dish. Use a fork or toothpick to prick some holes in it before baking. Bake for 12 minutes and allow to cool.
- While the shortbread layer bakes/cools, start on the lemon layer. Whisk the egg yolks in a small, heat-safe bowl and set aside.
- In a small saucepan, whisk together the lemon juice and honey. Heat the mixture over medium heat while occasionally whisking until hot but not boiling. (You should see steam rise from the sides of the pot.)
- Remove from heat and pour a small amount of the lemon mixture into the egg yolks whisk vigorously whisking in order to slowly warm the eggs. Pour this egg mixture back into the sauce pan, continuing to whisk.
- Resume heating the mixture over medium heat for another 4-5 minutes or until the mixture has thickened slightly. Dissolve the gelatin into the mixture then transfer to the refrigerator.
- Check on the lemon mixture every 20 minutes or so. Once cooled (but not set/firm), it can be poured over the shortbread layer. Place back in the refrigerator until the lemon layer sets up.
- Top with powdered sugar or other toppings/garnishes, if desired. Slice into 9 squares and serve.