Whole Wheat Apple Muffins

Ingredients

• 1 cup (4 ounces) whole wheat flour
• 1 cup (4 1/4 ounces) all-purpose flour
• 1 teaspoon baking powder
• 1 teaspoon baking soda
• 1/4 teaspoon salt
• 1 tablespoon cinnamon
• 1/2 cup (1 stick, 4 ounces) unsalted butter, at room temperature
• 1/2 cup (3 1/2 ounces) granulated sugar
• 1/2 cup dark brown sugar, packed, divided
• 1 large egg, lightly beaten
• 1 cup (8 ounces) buttermilk or yogurt
• 2 large apples, peeled, cored, and coarsely chopped