Rhubarb Blueberry Muffins

Ingredients (10)

• 1/4 cup butter, softened
• 3/4 cup sugar
• 1 egg
• 1/4 cup sour cream
• 1-1/2 cups all-purpose flour
• 2 teaspoons baking powder
• 1 teaspoon salt
• 1/3 cup milk
• 1 cup fresh or frozen blueberries
• 1 cup chopped fresh or frozen rhubarb