Peel the onion. Slice it into fairly thin slices, as shown in the video below. Separate the slices into rings.
Heat the olive oil in a large nonstick skillet over medium heat until it shimmers, about 2 minutes.
Add the onion rings to the oil. Use a wooden spoon to spread them evenly in the skillet. Sprinkle them with salt.
Cook the onions, stirring frequently, until they are soft and golden-brown, about 10 minutes.
I have a large nonstick skillet that I always use when making this recipe. I haven't experimented with other types of skillets (such as stainless steel), so I can't tell you if the onions might stick to other surfaces or if you'd need to use more oil. I wrote this recipe assuming you would use a nonstick skillet.