Preheat your oven to 350°F (175°C).

Line a muffin tin with paper liners or grease it with butter.

In a bowl, mix together the flour, granulated sugar, brown sugar, baking powder, ground cinnamon, and salt.

In another bowl, whisk together the oil, egg, and milk until well blended.

Pour the wet ingredients into the dry ingredients and stir until just combined.

Gently fold in the chopped apple.

Spoon the muffin mixture into the prepared muffin tin, filling each cup about 2/3 full.

In a small bowl, combine ¼ cup sugar, 2 tablespoons flour, 2 tablespoons butter, and 1 teaspoon cinnamon to make the topping.

Sprinkle the topping over the muffin batter.

Bake in the preheated oven for 20-25 minutes, or until a toothpick comes out clean.

Let the muffins cool in the tin for a few minutes before transferring them to a wire rack to cool completely.