In a large bowl, whisk together flour, baking powder, baking soda, and salt until well blended.
In a separate bowl, whisk together melted butter, oil, buttermilk, eggs, sugar, and vanilla until smooth and combined.
Add the dry ingredients to the wet ingredients and mix just until the last of the dry ingredients disappear. If you have time let the muffin batter rest for 15 minutes while you preheat the oven to 425°F and line a muffin pan with paper liners that have been lightly spritzed with nonstick spray.
Add ⅔ of the apple pie filling to the rested muffin batter and fold just until the apples are even distributed and there are ribbons of cinnamon sugar mixture throughout.
Distribute the batter evenly between the 12 muffin wells. Top each with about a teaspoon more of apples, and about a tablespoon of streusel topping.
Bake at 425°F for five minutes and then, without opening the oven door, turn the oven down to 350°F and bake for another 15 to 18 minutes or until a skewer or toothpick inserted into one of the middle muffins comes back clean or with just a few moist crumbs.
Let cool in the pan for five minutes then carefully transfer to a wire rack and let them cool as long as you can stand it. Dust with a little powdered sugar and enjoy.