1. Wash and peel the potatoes, then slice them into even pieces (or half-moons) for consistent cooking.
2. In a medium pot, bring water to a boil and cook the eggs.
3. Season the potatoes with a little salt, then steam them. Cover the pot to speed up the cooking process.

Prepare the Vinaigrette:

1. In a bowl, combine freshly squeezed lemon juice with salt, stirring until the salt dissolves (salt doesn’t dissolve well in oil!).
2. Add oil and mayonnaise to the bowl, and whisk everything together. Taste and adjust the seasoning if needed.

Assembling the Salad:

1. Once the potatoes are cooked, remove them from the steam basket and let them cool slightly.
2. Peel the eggs and slice them.
3. Peel and slice the red onion (into rings or strips, depending on your preference).
4. In a large salad bowl, combine the potatoes and vinaigrette, mixing well.
5. Add the eggs, onion, tuna, and olives (if using), or let everyone top their salad with their favorite ingredients.