Salsa: In bowl, combine tomatoes, green pepper, onion, coriander, oil, vinegar, salt and pepper; set aside.
In bowl, whisk together eggs, 2 tbsp (25 mL) water, salt and pepper just until blended but not frothy.
In 8-inch (20 cm) nonstick skillet, melt 1 tsp (5 mL) of the butter over medium heat. Pour one-quarter of the egg mixture into skillet; cook until almost set, gently lifting edge with spatula to allow any uncooked eggs to flow underneath, about 3 minutes.
Spoon 1/3 cup (75 mL) of the salsa onto half of the omelette; sprinkle 2 tbsp (25 mL) of the cheese over salsa. Fold uncovered half over top; cook for 2 minutes. Slide onto plate. Repeat with remaining ingredients. Serve with remaining salsa.