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 bowl, thoroughly whisk Greek yogurt, eggs, honey or maple syrup, olive oil or melted coconut oil, and vanilla extract until the mixture is smooth.
03 - In a medium bowl, blend whole wheat flour, baking powder, baking soda, ground cinnamon, and salt.
04 - Gradually add dry ingredients to the wet mixture, stirring gently just until combined. Do not overmix.
05 - Carefully fold diced apples and chopped nuts (if desired) into the batter until evenly distributed.
06 - Spoon batter evenly into prepared muffin cups, filling each about three-quarters full.
07 - Bake muffins for 18 to 22 minutes until golden and a toothpick inserted in the center comes out clean.
08 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.