01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or lightly coat with oil spray.
02 - In a large mixing bowl, whisk together the Greek yogurt, eggs, honey (or maple syrup), oil, and vanilla until the mixture is smooth.
03 - In a medium bowl, stir together whole wheat flour, baking powder, baking soda, cinnamon, and salt until well blended.
04 - Add the dry ingredients to the wet mixture and gently fold together just until incorporated. Avoid overmixing to keep the muffins tender.
05 - Fold in the diced apples along with walnuts or pecans if desired, ensuring even distribution throughout the batter.
06 - Spoon the batter evenly into the prepared muffin cups, filling each about three-quarters full. Bake for 18 to 22 minutes or until a toothpick inserted into the center of a muffin comes out clean.
07 - Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.