1. Line a large, flat baking pan with parchment paper and preheat the oven to 350 degrees.
2. Beat the eggs with the milk until they are well mixed and then add the flour and beat again. Pour this mixture into the baking pan.
3. Sprinkle the ham, tomato and onion evenly over the length of the egg mixture. Cover this with ½ cup of the shredded cheese. Mozzarella or cheddar are good choices.
4. Put the pan carefully in the pre-heated oven and bake for 10-15 minutes or until the edges are firmly set.
5. Remove the pan from the oven and add the remaining cheese.
6. Bake for an additional 2-3 minutes.
7. Carefully roll the finished omelet using forks or a spatula so you do not burn your fingers. Transfer the roll to an elegant platter and slice to serve.