Peel the potatoes and chop them on rough chunks, and then put them in a pot.
Add water to the pot so that it covers all the potatoes. Put the pot on high heat and wait for the water to start boiling
Boil the potatoes for 20-30 minutes (TIP: One way to know for sure if the potatoes are boiled is to poke the largest potato with a fork all the way through the middle and hold the fork downwards. If the potato falls down smoothly it’s cooked, otherwise it’s not).
Next, drain the boiled potatoes from the water and put them in a bowl. Chop the onion on half circles and add it to the potatoes.
Add the Olive oil and the vinegar or lemon juice (I prefer vinegar for this salad, but it’s up to you) and then season with a teaspoon of salt and a pinch of pepper.