Add butter or oil to a large non-stick or cast-iron skillet over medium-high heat; swirl around until butter melts and begins to bubble.
Crack one egg into a dish, then gently slide egg into pan (try not to break the yolk); repeat with remaining eggs. Season with salt and pepper to taste.
Fry until edges of egg whites begin to turn golden and lacy, about 3 minutes.
Sunny-side-up eggs are usually served with a bit of uncooked white clinging to the yolk; to cook it a bit on top, tip the pan so the butter pools, dip a spoon in and baste the yolks with hot butter until the clear white turns slightly opaque.
Using a flat spatula, lift out eggs and transfer to plate; serve with buttered toast.
Serve sunny-side-up eggs over a lightly dressed salad of field greens and chopped bacon.