• Preheat the oven to 400F. Grease a 12-cup muffin tin with baking spray or line with cupcake papers.

For the Topping:

• In a medium bowl, stir together the brown sugar, flour, granulated sugar, and cinnamon. Stir in the melted butter with a fork, until the mixture is combined but still clumpy. Set aside.

For the Muffins:

• In a medium mixing bowl, whisk together the flour, baking powder, cinnamon, and salt.
• In another medium mixing bowl, toss the apples with two tablespoons of the flour mixture until the apples are well coated.
• In a large mixing bowl, beat the butter and sugars together on medium speed until creamy, about 2 minutes. Add the eggs, one at a time, beating until well combined. Scrape down the bowl and beat in the vanilla.
• With the mixer on low speed, add a third of the flour mixture, followed by half of the milk. Continue alternating between the flour and milk, mixing just until combined. Fold in the apples. Divide the batter among the wells of the muffin pan, about ⅓ cup per muffin. (They will be mostly full.) Sprinkle the topping evenly over the batter, about 2-3 tablespoons per muffin.
• Bake for 10 minutes.
• Reduce the oven temperature to 350F and continue baking for 12 to 15 minutes or until a toothpick inserted into the center comes out with a few moist crumbs. Let cool for 10 minutes in the pan then remove and continue cooling on a wire rack. Muffins can be stored in an airtight container at room temperature for up to 3 days.