Beat the egg yolk with a wire whisk or fork.
Melt butter in a frying pan and add beaten egg yolk to it. Swirl the pan gently to spread the egg a little, but not too thin.
Now scatter the vegetables over the omelette.
Season with black pepper powder. Lightly press the veggies on the omelet using a flat spatula.
Once the omelette's bottom is cooked, flip and cook on the other side.
Let the omelette cool down a bit before serving.