Heat butter in a small skillet and pour in half of the eggs. Sprinkle with half of the grated Gruyère and cook over medium-low heat. F
Fold the omelette in half and transfer to a plate. Set aside. Make another omelette with the remaining eggs and cheese.
Place lettuce on the tortilla bread. Arrange the omelette, tomato, avocado, red onions and cress on top. Sprinkle with salt and pepper. Roll the tortilla into a wrap and cut in half.