½cupchopped nutssuch as pecans or walnuts, and/or additional nuts for topping (optional)
Preheat oven to 400°F. Line 12 muffin cups with paper liners and lightly spray liners with nonstick spray.
Measure oats into a blender. Blend until the oats are ground into a fine powder, like flour. Shake the ground oats to one side of the pitcher and add the baking powder, cinnamon, baking soda, salt, applesauce, honey, Greek yogurt, eggs, and vanilla to the blender. Turn on the blender to low speed and then immediately increase to high speed. Blend until the ingredients are just combined, stopping and scraping down the sides of the blender as necessary. If using nuts, add them at the very end; sprinkle them on top of the finished batter and quickly pulse one time to incorporate the nuts without chopping them further.
Evenly divide the batter between the prepared muffin cups, pouring it directly from the blender pitcher. If desired, sprinkle the top of each muffin with additional chopped nuts. Bake for 18 to 22 minutes or until the muffins test done with a toothpick. Allow the muffins to cool in the pan for 5 minutes, and then transfer them to a wire rack to finish cooling.