Spray a 9” square baking pan with cooking spray and line pan with parchment paper, leaving enough extra to extend over the sides.
Combine dry ingredients in the bowl of your food processor and process until broken down to a coarse grainy texture. Add wet ingredients and process until well combined.
Pour into prepared baking pan and spread uniformly all the way to the sides to form a crust. The mixture will be rather sticky and hard to spread; To make the process easier, use a rubber spatula dipped in water.
Bake this crust for 12-15 minutes, or until nice and golden brown; remove from oven and set on wire rack to cool.
For the filling
Soak the sheets of gelatin in a bowl of icy cold water for 5-10 minutes, until soft (if using powdered, use ½ cup of the coconut water to bloom your gelatin)
Meanwhile, add lemon zest, coconut flour, arrowroot flour and protein powder to the bowl of your food processor and give this a quick spin to combine. Reserve.
Bring coconut water and lemon juice to a simmer; immediately remove from heat.
Lift gelatin sheets from cold water bath and gently wring to remove excess water; add to hot liquid and stir until completely dissolved (if using powdered, add bloomed gelatin along with blooming liquid and stir until dissolved).
Add buttermilk to flour mixture and process until well combined.
While motor is turning, pour in lemon juice and gelatin mixture and again, process until well incorporated.
Transfer that mixture to a large bowl and place in the refrigerator to cool until almost completely set but still on the soft side, about 3 hours.
Give the lemon mixture a quick stir with a whisk to smooth it out and pour over reserved crust; Delicately spread the mixture all the way to the sides of the pan.
Sprinkle unsweetened shredded coconut overtop and put this back in the refrigerator to set completely, at least 8 hours but preferably overnight.
Using the edges of the parchment paper, remove from pan and cut into 9 individual squares. (or more if you want smaller bars)
These squares will keep in the refrigerator in an airtight container for up to a week.