Buttermilk Blueberry Muffins

This recipe is based on Mollie Katzen's recipe of the same title from her cookbook, Sunlight Cafe. I have made a couple of alterations, including increasing the amount of lemon zest, vanilla extract and blueberries.
Ingredients:
2 1/2 cups unbleached all-purpose flour
3/4 teaspoon salt
1 1/2 teaspoons baking powder
1/4 teaspoon baking soda
1/2 cup unbleached cane sugar
2 tablespoons grated lemon zest
1 1/2 cups buttermilk
2 tablespoons fresh lemon juice
1 large egg
1 1/2 tablespoons vanilla extract
4 tablespoons (1/2 stick) unsalted butter, melted
1 2/3 cups frozen wild blueberries

Instructions:

1. Preheat oven to 375.
2. Combine first 6 ingredients in a large bowl. Set aside.
3. Place buttermilk in a medium size bowl. Add the lemon juice, egg, and vanilla extract. Mix until combined.
4. Pour buttermilk mixture and butter (melted) into the dry ingredients. Stir until combined then fold in blueberries (still frozen) until mixed. Note: If batter is too dry, you may need to add additional buttermilk, 1 tablespoon at a time.
5. Spray muffin tin (12 muffin cups) with non-stick spray and fill muffin cups all the way full.
6. Bake for 22-26 minutes until toothpick comes out clean. Cool on rack for 30 minutes before serving.

Nutrition Facts: Serving size = 1 muffin; Calories 208, Calories from Fat 43, Total Fat 4.8g, Saturated Fat 2.8g, Cholesterol 29mg, Sodium 283mg, Potassium 105mg, Total Carbohydrate 36.7g, Dietary Fiber 1.5g, Sugars 15.9g, Protein 4.4g.