Preparation

• Begin by warming your oven to 375°F. Prepare a 12-count muffin pan by either greasing it with nonstick spray or inserting cupcake liners.
• Using either a stand mixer fitted with the paddle attachment or a handheld mixer, beat together the butter, granulated sugar, and brown sugar until the mixture becomes fluffy, a process that usually takes about 5 minutes.
• In a small bowl whisk the flour, baking powder, baking soda, salt, and cinnamon.
• Add the egg and mix until combined. Scrape down the sides with a spatula, then slowly pour in the buttermilk, stirring until fully incorporated. Finally, add the dry ingredients and mix until well combined.
• Using a spatula fold the apples into the batter. Spoon the batter into the prepared muffin pan.
• In a medium bowl, mix brown sugar, granulated sugar, and cinnamon. Gently blend in the melted butter and flour with a fork, aiming for large crumbles. Sprinkle this mixture over the muffin batter in the pan and gently press it down so it sticks.
• Bake for 25 to 30 minutes or until a toothpick inserted in the center comes clean. Let muffins rest in the pan for 5 minutes before moving to a cooling rack to finish cooling.