In a bowl, mash the banana thoroughly with a fork. Mix in the cinnamon and vanilla extract until combined. Add the eggs and whisk well until smooth.
Heat a non-stick frying pan over medium-low heat. Melt the butter, spreading it evenly across the pan.
Pour the egg mixture into the pan and sprinkle the raisins (or chocolate chips) evenly on top.
Cover the pan with a lid and cook for about 4 minutes, or until the edges are set.
Slide the omelet onto the lid, flip it back into the pan to cook the other side, and cook for another 3 minutes until fully set.
Transfer the omelet to a plate. Top with Greek yogurt, a drizzle of maple syrup, and a sprinkle of cinnamon.
Tip: Keep the heat on medium-low so the natural sugars in the banana don't burn before the eggs fully cook through!