Coat an 10-inch nonstick skillet with flared sides with cooking spray. Heat skillet over medium heat.
In a large bowl beat eggs, chives, salt, and cayenne pepper with a whisk until frothy. Pour into prepared skillet. Immediately begin stirring egg gently but continuously with a heat-resistant spatula until mixture resembles small pieces of cooked egg surrounded by liquid egg. Stop stirring. Cook 30 to 60 seconds more or until egg is set and shiny.
Sprinkle cheese over half of the omelet. Top with 1 cup of the spinach and 1/4 cup of the Red Pepper Relish. Using spatula, fold omelet partially over filling. Arrange remaining 1 cup spinach on a warm platter. Transfer omelet to platter and top with remaining relish.
Red Pepper Relish
In a small bowl combine pepper, green onion, vinegar, and black pepper.