In a medium bowl, whisk together the gluten free flour, sugar, baking powder, baking soda, and salt.: The dry mix should smell faintly sweet and slightly bready, and you will notice the texture shift as the finer leaveners blend in. Whisking aerates the mix, which helps the pancakes lift during cooking. If you see clumps, press them against the bowl with the whisk to break them up; stubborn lumps are a common mistake and lead to uneven pockets in the batter.
In a large bowl, whisk together the milk, egg, melted butter, and vanilla extract.: As you whisk, the mixture should look smooth and glossy, with small ribbons forming briefly from the egg. The cooled melted butter will add a sheen without cooking the egg, which preserves a tender texture. If the butter is warm and you see bits of cooked egg or curdling, you warmed the butter too much; start again with a fresh egg for the best result.
Add the flour mixture to the wet ingredients and stir together until just combined. The batter will still be slightly lumpy. Cover the bowl with plastic wrap and let rest for 20 minutes.: After mixing, the batter should be thick yet pourable, with small lumps that will smooth out as the flours hydrate. Resting allows the flour particles to absorb liquid, which improves texture and reduces a chalky aftertaste. Avoid overmixing here, because that can make the pancakes dense; a common error is stirring until perfectly smooth, which actually harms tenderness.
Heat a skillet over medium heat or a griddle to 375°F, and lightly coat the pan with oil or cooking spray. Add about 1 tablespoon of batter or a small cookie scoop full for each pancake, leaving some space between each one. Cook until you see that the edges are turning golden-brown and bubbles are appearing at the surface, about 2-3 minutes. Flip and cook until the other side is golden, about 1-2 minutes.: When the pan reaches the right temperature, a few drops of water should dance and evaporate quickly. The hot surface creates immediate contact browning, forming a golden crust that contrasts with a soft interior. If the pan is too cool, pancakes will spread thin and remain pale; if it is too hot, they will brown too fast and stay raw inside. Adjust the heat as needed and test with a small pancake first.
Remove the pancakes from the pan and repeat with the remaining batter.: Look for a gentle sizzle when the batter hits the pan, and notice how the batter forms neat, round disks. Small scoops allow even cooking and quick flipping. Crowding the pan is a frequent mistake, it lowers the temperature and causes uneven browning and steaming instead of searing.
Cook until you see that the edges are turning golden-brown and bubbles are appearing at the surface, about 2 to 3 minutes.: You will hear a soft sizzling and see small bubbles form and pop on the surface; that is the signal the interior is setting. The edges should look set and slightly dry before flipping. If you flip too early, the pancake may collapse and remain undercooked inside, which is a common timing error for busy cooks.
Flip and cook until the other side is golden, about 1 to 2 minutes.: After flipping, watch for an even golden tone on the cooked side, and listen for a slightly lower-pitched sizzle as moisture decreases. The second side cooks faster, so stay close to avoid over browning. Overcooking will dry the interior and make the texture crumbly instead of tender.
Remove the pancakes from the pan and repeat with the remaining batter.: As you transfer pancakes to a plate, the stack will steam slightly; I like to place them in a single layer briefly to prevent sogginess, then stack right before serving. If you leave them too long piled up while still steaming, the bottoms can soften and lose crispness. Keep the pan at a steady temperature between batches so each pancake finishes consistently.