Beat eggs in medium bowl. Add milk, dill, pepper and salt; beat well.
Melt butter in medium nonstick skillet over medium-low heat. Add onions; cook and stir 2 to 3 minutes or until crisp-tender. Add egg mixture; gently stir in salmon. Cook until eggs are set but still moist, stirring constantly.
Sprinkle cheese over eggs. Cover; cook 1 minute or until cheese is melted.