Preheat oven to 375 degrees F.
Line muffin tin with paper liners
In a large mixing bowl add ground flaxseed and water. Stir to mix well and let sit for 5 minutes.
In a small bowl mix together 1/4 sugar and 2 tsp cinnamon. Set aside for later.
When 5 minutes wait time is up for flaxseeds, add sugar to the flaxseed mixture and stir to combine.
Melt butter and whisk it into the flaxseed mixture.
Add vanilla and whisk together.
Stir in almond flour, brown rice flour, potato starch, baking powder, and salt. Mix until mixture is smooth. The batter will have a thick consistency.
Spoon 1 Tbsp of batter into each muffin cup and lightly spread to cover the bottom.
Sprinkle 1/2 tsp of cinnamon sugar mixture over each.
Fill the muffin cups with the remaining batter 3/4 full.
Sprinkle 1/2 tsp of cinnamon sugar mixture over each muffin.
Bake for 28 minutes or until a toothpick comes out clean when inserted into the center of a muffin.
Remove from the oven and let muffins sit for 5-7 minutes on a cooling rack.
Remove muffins from the muffin tin with papers still on and continue to cool on a wire rack.