1.In An 8-In. Skillet, Saute Tortilla In Butter Until Softened, About 2 Minutes. Meanwhile, Beat Eggs, Water And Salt In A Bowl. Pour Over Tortilla In Skillet; Cook Over Medium Heat. As Eggs Set, Lift Edges, Letting Uncooked Portions Flow Underneath. When Eggs Are Set, Remove From The Heat. Sprinkle With 3/4 Cup Cheese. Combine Avocado, 1/2 Cup Sour Cream, Chiles And Lemon Juice; Spread Over Half Of The Omelet. Fold Omelet In Half And Transfer To A Warm Platter. Top With Tomato And Remaining Cheese And Sour Cream.