Combine the Dijon mustard and sour cream in a small bowl. Mix and set aside.
Heat a 10” skillet over medium heat. Coat lightly with olive oil spray. Pour egg whites into pan and swirl around to fully cover the pan in an even layer.
Season the egg whites with salt and pepper. Add in the salmon in a vertical strip down the center (reserve some for garnish) and top with the Dijon/sour cream mixture. Sprinkle dill over entire egg reserving some for garnish.
Fold the left side of the egg over the center strip then the right side over the center strip, creating a tri-fold omelette. Transfer onto plate and garnish with remaining dill, remaining salmon, tomatoes, and additional pepper.