Preheat the oven to 380 F. Use a silicone 7 inch oven proof dish or silicone pie pan. Push large tortilla in the bottom, covering up the sides of the dish too to contain filling.
In a bowl, combine all ingredients, but only add half of the cheese into the filling. You can also save some of the green onions for serving too.
Mix everything thoroughly and carefully transfer it to the tortilla, trying not to let the omelet mixture spill over the edges. Bake for 20 minutes.
Remove from the oven and sprinkle the remaining cheese on top. Return to the oven for another 5 minutes until melted and golden brown. Remove, let it cool a little, then serve with extra green onions and, if desired
In muffin tin - Use a 4" biscuit cutter to cut 3 rounds out of each large tortilla to push 1 into each sprayed muffin tin hole. Pour in egg mixture to fill 3/4 of the way full. Bake in preheated oven at 350 degrees for 20-23 minutes or until set in the center.