01 - Preheat oven to 375°F. Line a 12-cup muffin pan with paper liners or grease lightly with oil spray.
02 - In a large mixing bowl, whisk together Greek yogurt, eggs, honey (or maple syrup), oil, and vanilla extract until fully blended.
03 - In a medium bowl, stir together whole wheat flour, baking powder, baking soda, ground cinnamon, and salt.
04 - Add the dry mixture to the bowl with wet ingredients and stir gently until just combined. Do not overmix.
05 - Gently fold in diced apples and nuts, if using, ensuring even distribution throughout the batter.
06 - Divide the batter evenly among the prepared muffin cups, filling each about three-quarters full.
07 - Bake for 18 to 22 minutes, or until a toothpick inserted in the center comes out clean.
08 - Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.