Step 1

Arrange a rack in the middle of the oven and heat the oven to 375°F. Line a standard 12-well muffin pan with paper liners or coat the wells with cooking spray.

Step 2

Whisk 2 1/2 cups all-purpose flour, 1/2 cup of the granulated sugar, 2 teaspoons baking powder, 2 teaspoons of the ground cinnamon, and 1/2 teaspoon kosher salt together in a large bowl. Stir the remaining 4 teaspoons granulated sugar and 2 teaspoons ground cinnamon together in a small bowl and set aside for the topping.

Step 3

Place 1 1/4 cups whole or 2% milk, 1/2 cup neutral oil, 1 large egg, and 1 teaspoon vanilla extract together in a medium bowl and whisk until combined. Core and dice 2 medium apples (peel first if desired, about 2 1/2 cups).

Step 4

Pour the milk mixture into the flour mixture and mix with a wooden spoon or rubber spatula until just combined. Some lumps are fine. Gently fold in the diced apple.

Step 5

Divide the batter between the muffin wells, about 1/3 cup of batter per well. Sprinkle each muffin with 1/2 teaspoon cinnamon-sugar.

Step 6

Bake until the muffins are golden-brown and a toothpick inserted into the center of a muffin comes out clean, about 20 minutes. Let cool for 5 minutes before removing the muffins from the pan.