Heat skillet over medium heat until hot. Add butter, if using.
While skillet is heating, crack eggs into a bowl and whip until frothy with a whisk or a fork.
Add eggs to hot pan. Cook, stirring frequently, until eggs are fluffy and cooked through, about 3 minutes. Remove from heat and stir in cheese. Season with salt and pepper, as desired.
Notes
Variations: try this with other varieties of cheese to change it up.