Saute spinach and onion in the olive oil on medium heat in a non stick skillet for about 2 minutes on medium high heat or until the spinach has wilted. Season with salt and pepper. Stir in tomatoes. Reduce heat to low and simmer for about five minutes.
While vegetables are simmering, beat together eggs, salt, pepper, and cream until it's smooth.
Add the egg mixture to pan, distributed evenly. When underside is cooked, add the feta cheese to the top. Reheat the gyro meat in the microwave for 15 seconds at a time till hot then add to the omelet.
To serve, fold one edge up and slide out of the pan so it inverts onto a platter tri-folded into an burrito shape. Serve with tzatziki sauce on the side.