Omelet Filling: Heat oil in a sauté pan over high heat. Add onion; cook until lightly charred and tender, about 5 minutes, stirring frequently. Stir in salami, spinach and sun-dried tomatoes; remove from heat and let stand until spinach wilts, about 3 minutes, stirring frequently. Cool; refrigerate in an airtight container up to 3 days. Makes about 4 cups.

For serving, reheat 1 cup Omelet Filling. Heat 1 tablespoon oil in a nonstick sauté pan over high heat. Add 5 salami slices and cook until crisp, about 1 minute, turning once; drain salami on paper towel-lined plate. Wipe out pan; add 1 tablespoon oil and heat over medium-low heat. Whisk 3 eggs and 2 tablespoons milk in a bowl; add to hot pan and swirl to coat. Cook until eggs are just set, lifting the edges lightly with heat-proof spatula to allow egg-mixture to cook evenly, about 5 minutes. Sprinkle omelet with 1/4 cup cheese and 1/4 teaspoon pepper; cover and cook until cheese melts and internal temperature of omelet reaches 160°F, about 1 minute. Place warm Omelet Filling over half of the omelet; gently fold omelet over filling. Serve omelet garnished with crisped salami slices, and 1/2 teaspoon each parsley and Parmesan cheese.