Step 1 - Preheat and Prep
Preheat your oven to 425°F (220°C). Yes, that's hotter than most muffin recipes. Starting at a higher temperature creates a burst of steam inside the muffin that pushes the top up quickly, creating that tall, domed bakery-style crown. You'll drop the temperature after a few minutes more on that below.
Line your muffin tin with liners and spray lightly with cooking spray. Make your flax eggs and set them aside to gel. Stir the apple cider vinegar into your non-dairy milk and set aside for 5 minutes.
Step 2 - Combine Dry Ingredients
In a large bowl, whisk together the gluten-free flour, baking powder, baking soda, salt, sugar, and lemon zest. Whisk thoroughly lumpy dry ingredients create uneven muffins with pockets of baking powder that taste metallic.
Step 3 - Combine Wet Ingredients
In a second bowl, whisk together the flax eggs (now gelled), the "buttermilk" mixture, oil, vanilla extract, and lemon juice. Whisk until fully combined and slightly emulsified.
Step 4 - Fold Together Gently
Pour the wet ingredients into the dry ingredients and use your silicone spatula to fold gently until just combined. Stop mixing the moment no dry flour is visible. Gluten-free batters don't develop gluten, so you can't really "overmix" the way you can with conventional flour but overworking the batter breaks down the air bubbles from your baking powder and leavening, which deflates your muffin dome. A few small lumps are completely fine.
Fold in the blueberries last, using 2–3 gentle strokes. Coat them in batter rather than crushing them.
Step 5 - Portion and Top
Use an ice cream scoop to fill each muffin cup approximately ¾ full. For bakery-style height, fill cups slightly higher almost to the top. Sprinkle coarse sugar over each muffin top generously.
Step 6 - The Two-Temperature Bake
Place muffins in the 425°F oven for exactly 5 minutes. Then without opening the oven door drop the temperature to 375°F (190°C) and bake for a further 17–20 minutes until a toothpick inserted into the center comes out clean. This two-temperature method is the professional bakery trick that creates the high dome without burning the tops or undercooking the center.
Step 7 - Cool Before Eating (Yes, Really)
Let muffins cool in the tin for 5 minutes, then transfer to a wire rack. Gluten-free muffins need the full cooling time to set their crumb structure cutting into them while still hot produces a gummy, underset interior that feels undercooked even when it isn't. Wait at least 15 minutes.