Preheat oven to 400°. In a large bowl, combine the flour, sugar, baking powder and salt. In a small bowl, combine the eggs, buttermilk and butter; stir into dry ingredients just until moistened. Fold in blueberries.
Fill greased or paper-lined muffin cups three-fourths full. Bake until a toothpick inserted in the muffin comes out clean, 20-24 minutes. Remove to a wire rack to cool.
To substitute for each cup of buttermilk, use 1 Tbsp. white vinegar or lemon juice plus enough milk to measure 1 cup. Stir, then let stand 5 min. Or, use 1 cup plain yogurt or 1-3/4 teaspoon cream of tartar plus 1 cup milk.