Step 1: In a large mixing bowl, whisk together the gluten-free all-purpose flour blend, granulated sugar, baking powder, baking soda, and salt. If your gluten-free flour blend does not contain xanthan gum, add 1/2 teaspoon now. Whisk thoroughly to ensure even distribution of leavening agents.
Step 2: In a separate medium bowl, whisk together the buttermilk, large egg, melted unsalted butter (ensure it's not too hot), and pure vanilla extract.
Step 3: Pour the wet ingredients into the dry ingredients. Add the apple cider vinegar. Stir gently with a whisk or spatula just until combined. Do not overmix; a few lumps are fine.
Step 4: Let the batter rest for 5-10 minutes. This allows the flours to hydrate and the leavening agents to begin working, contributing to fluffier pancakes.
Step 5: While the batter rests, heat a non-stick griddle or large skillet over medium-low heat. Lightly grease the griddle with butter, oil, or cooking spray.
Step 6: Pour about 1/4 cup of batter per pancake onto the hot griddle. Cook for 2-3 minutes per side, or until golden brown and bubbles begin to form and pop on the surface. The edges should look set. Flip carefully and cook for another 1-2 minutes on the second side.
Step 7: Serve your fluffy gluten-free pancakes immediately with your favorite toppings. To keep remaining pancakes warm, place them on a baking sheet in a warm oven set to 200°F (95°C).