Preheat your waffle iron according to the manufacturer’s directions. Lightly grease the plates if necessary.
In a large bowl, whisk together the gluten-free flour blend, sugar, baking powder, and salt.
In a separate medium bowl, whisk the milk, eggs, melted butter, and vanilla extract until combined.
Pour the wet ingredients into the dry ingredients. Mix gently until just combined. Do not overmix; a few lumps are acceptable for fluffiness.
If using frozen blueberries, toss them lightly with 1 teaspoon of the dry flour mixture before adding them to the batter. This helps prevent sinking.
Gently fold the coated blueberries into the batter.
Pour the batter onto the hot waffle iron, filling it according to your iron’s capacity. Cook until golden brown and steam subsides, usually 4 to 6 minutes.
Carefully remove the waffle. Repeat with the remaining batter. Serve immediately or keep warm in a low oven (200°F) while finishing the batch.
Notes
For extra crispy edges, brush the waffle iron plates lightly with oil or melted butter before pouring each batch of batter.
If your gluten-free flour blend does not contain xanthan gum, add 1 teaspoon to the dry ingredients.
If you prefer dairy-free waffles, substitute regular milk with almond or soy milk and use a dairy-free butter substitute.
To prevent color bleeding from the blueberries, avoid stirring the batter excessively after adding them.