Rhubarb Muffins

Ingredients (15)

• 1 egg
• 1-1/4 cups packed brown sugar
• 1 cup buttermilk
• 1/2 cup vegetable oil
• 2 teaspoons vanilla extract
• 2-1/2 cups all-purpose flour
• 1 teaspoon baking soda
• 1 teaspoon baking powder
• 1/2 teaspoon salt
• 1-1/2 cups diced fresh rhubarb
• 1/2 cup chopped walnuts
• TOPPING:
• 1/3 cup sugar
• 1 teaspoon ground cinnamon
• 1 teaspoon butter, melted