Preheat your oven to 450°F. Line a 12-cup muffin pan with paper liners or lightly grease each cup.

Step 2: Combine the Dry Ingredients
In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt.

Step 3: Add the Apples
Add the finely chopped apples to the dry ingredients and gently toss them together until the apples are evenly coated. Set aside.

Step 4: Cream the Butter and Sugars
In a large mixing bowl, beat the softened butter, brown sugar, and granulated sugar together until light and creamy.

Step 5: Add the Eggs and Wet Ingredients
Add the eggs one at a time, mixing well after each addition. Then mix in the Greek yogurt or sour cream, buttermilk, and vanilla until smooth and well combined.

Step 6: Combine the Batter
Add the dry ingredients and apples to the wet mixture. Gently mix just until everything is combined. Be careful not to overmix the batter.

Step 7: Make the Crumb Topping
In a small bowl, combine the melted and slightly cooled butter, flour, brown sugar, granulated sugar, cinnamon, and salt. Stir with a fork until the mixture forms coarse crumbs.

Step 8: Fill the Muffin Cups
Divide the batter evenly between the 12 muffin cups, filling them generously. Sprinkle the crumb topping over each muffin, gently pressing it into the batter if needed.

Step 9: Start Baking at High Heat
Place the muffins in the 450°F oven and bake for 5 minutes. This initial burst of high heat helps the muffins rise and gives them those tall, bakery-style tops.

Step 10: Lower the Temperature and Finish Baking
Without opening the oven, reduce the temperature to 350°F. Continue baking for about 20 minutes, or until the tops are golden and a toothpick inserted into the center comes out clean.

Step 11: Cool and Serve
Let the muffins cool in the pan for about 5 minutes, then transfer them to a cooling rack. Serve warm or allow them to cool completely before storing.