Soak the lentils in the water for 6 hours at room temperature.
Drain the lentils and rinse to remove starchy residue.
Pulse purée the lentils in a vitamix blender or equivalent.
Create a smooth, thick batter by streaming in cold water (about 10 oz.) with the blender on high.
Whisk together the lentil purée and sifted rice flour in a large stainless steel bowl.
Add the remaining water (14 oz.) and whisk until smooth.
Ferment the mixture in a non-reactive storage container about twice the volume of the batter. Cover with plastic wrap and let it rest at room temperature overnight. NOTE: The batter isn’t ready until there are noticeable air bubbles throughout the batter. This could take two days (or warmer air temperature).
Refrigerate the fermented batter until needed for service.