Preheat your waffle iron. Combine the flax seed and water in a small bowl, set aside. Combine the almond milk and apple cider vinegar in a measuring cup, set aside. Add the flours, baking powder, salt, & sugar to a medium bowl and mix well. Melt the butter in another medium bowl. Slowly add the almond milk mixture to the butter, whisking vigorously while pouring it in. Add the flax mixture and the vanilla and mix well. Add the flour mixture to the butter mixture and mix well, until few lumps remain (but don't go too crazy). Cook the waffles according to your waffle maker's instructions.* Eat right away, or let cool on a wire rack and freeze in a zip-top bag for future enjoyment!