Using an 8-inch, non-stick skillet, melt butter over medium heat. Add beaten eggs. Add the eggs begin to coagulate, add the 3 cheeses evenly over the eggs. As cheese begins to melt, and before the eggs get brown, flip or turn egg mixture over. Continue to cook until the cheese melts. Turn omelette 1 more time. The finished omelette will be a nice yellow color with the cheese melted. Serve immediately.