Sauté spinach, mushrooms and leeks in oil until spinach is limp. Drain water from pan if necessary. Mix all together in big bowl. Heat the oil (Pam is fine) in the cast iron skillet. Place egg mixture in skillet on top of stove and cook until edges are bubbling. Place sliced tomatoes on top in a nice design before placing in oven. Cook for 1 hour, 45 minutes (+ or -)