- 1 1/4 cups milk
- 1 tablespoon vinegar
- 3/4 cup white sugar
- 1/2 cup butter, softened
- 2 eggs
- 1 egg yolk
- 1 tablespoon freshly grated lemon zest (optional)
- 1 1/2 cups rice flour
- 1 cup cornmeal
- 4 teaspoons baking powder
- 1/2 teaspoon salt
- 1 cup blueberries
- 1 tablespoon raw sugar, or to taste (optional)
- Preheat oven to 400 degrees F (200 degrees C). Line 12 muffin cups with paper liners.
- Stir milk and vinegar together in a small bowl; set aside to sour for 3 to 5 minutes.
- Beat white sugar and butter together in a bowl using an electric mixer until creamy and smooth. Add eggs, egg yolk, soured milk, and lemon zest; beat until smooth, scraping down sides of bowl as needed.
- Mix rice flour, cornmeal, baking powder, and salt in a bowl; slowly stir flour mixture into creamed butter mixture until just mixed. Gently fold in blueberries. Pour batter into the prepared muffin cups, filling each about 3/4 full. Sprinkle each muffin with raw sugar.
- Bake in the preheated oven until a toothpick inserted in the center of a muffin comes out clean, 18 to 20 minutes.