Heat butter in a small non-stick skillet over medium-high until melted and swirl the skillet to coat the bottom.
Crack the egg into the frying pan and immediately lower heat to medium-low. Cook until the whites are set for each egg cook: about 1 ½ - 2 minutes for over easy, 3 minutes for over medium and sunny side ups, about about 5 minutes for over hard.
For sunny side up, remove from heat when the whites are set but the yolk is still runny.
For over easy eggs, carefully flip and immediately remove from heat when the yolk and egg whites are still runny
For over medium eggs, carefully flip and continue cooking until the whites are cooked and yolk appears somewhat set, but jiggly in the middle, about 1 more minute.
For over hard eggs, carefully flip and continue cooking until the whites are cooked and yolks appear fully set, about 3 more minutes.
Season with salt and pepper and enjoy immediately.
Video
Notes
Reheat over hard fried eggs in a lightly oiled skillet. Use leftovers within one day, though they are best served fresh.