Blueberry Sourdough Muffins

Name: Blueberry Sourdough Muffins
Ingredients: 12 muffin paper liners; 2 cups all-purpose flour; 1 teaspoon ground cinnamon; 1 teaspoon baking soda; 3/4 teaspoon kosher salt; 1/4 teaspoon ground nutmeg; 1 cup sourdough starter, discard or fed; 3/4 cup packed light brown sugar; 1/4 cup canola oil; 1/4 cup milk; 1 large egg; 1 teaspoon vanilla extract; 2 cups fresh or frozen blueberries (do not thaw, 10 ounces); 2 tablespoons demerara or coarse sugar