Crack eggs, add half of the salt and beat eggs only until well-mixed.
Peel and small dice the onion and potatoes, into ¼” cubes. Keep the two ingredients separate.
Heat oil in a 10″ non-stick pan and slowly fry the onion. Fry until fragrant and translucent. Avoid browning the onion
Add potato, the other half of the salt, and pepper. Stir and continue cooking on medium heat until potato is just cooked.
Gently level off the top of the potato mixture and pour eggs into the pan. Shake the pan gently to allow the egg mixture to fill the pan.
Turn the heat down to low and put a lid over the pan to cook the eggs more evenly. When the eggs start to peel away from the sides, slide the whole egg-potato mixture out onto a big round plate.
“Flip” the omelette by putting another plate on top. While holding on to both plates, turn the plates upside down.
Slide the omelette back into the pan and cook for just a few more minutes on medium heat, uncovered.
Slide tortilla out onto a round plate, cut into wedges and serve. The omelette is great hot-off-the-pan, but it’s also just as good after it’s cooled down to room temperature.