Good-Cooking - Apple Muffins

Ingredients

• 1/2 cup butter (at room temperature)
• 1/2 cup brown sugar, packed
• 3/4 cup granulated sugar
• 2 eggs
• 2 1/4 cups buttermilk
• 4 cups flour
• 3 tablespoons ground cinnamon
• 1 tablespoon baking soda
• 1/2 teaspoon salt
• 2 cups peeled McIntosh apples, sliced in 1/2-inch pieces (2 to 3 medium)
• Additional brown sugar to top muffins