In a mixing bowl, combine the gluten-free flour, baking powder, and salt.
In another bowl, mix the warm milk, sugar, and yeast. Let it sit for 5 minutes until frothy.
Pour the yeast mixture into the dry ingredients and add the warm water. Whisk until smooth.
Cover the bowl and let the batter rest for 30 minutes.
Heat a frying pan over medium heat and grease the crumpet rings. Place the rings in the pan and pour batter into each ring until half full.
Cook until bubbles form on the surface and the edges look set, about 5-7 minutes. Remove the rings and flip the crumpets to cook the other side for 1-2 minutes.