In a small, safe, nonstick skillet, heat the oil over medium heat.

Add the onions, tomatoes and spinach. Cook until the onion is soft, about 3 to 5 minutes. Stir in a pinch of salt. Transfer the spinach mixture to a bowl. Cover and keep warm.

In a medium bowl, whisk the eggs and a pinch salt and pepper until frothy.

Spray coat a medium, safe nonstick skillet or omelet pan with cooking spray and heat over medium heat.

Add 1/2 of the eggs, swirling to evenly cover the bottom of the pan. Cook until set, about 1 1/2 to 2 minutes. Use a rubber scraper to gently lift the eggs up and allow the uncooked egg whites to flow underneath.

Spoon 1/2 of the spinach mixture onto half of the omelet, fold over, and slide onto a serving plate. Repeat with remaining eggs and spinach mixture.

Serve.