This isn't really a recipe. It's a habit. A reflex. The salad that appears beside every meal in Portugal, from the humblest tasca to the Sunday table.

Avó Leonor made this salad every single day. Lunch and dinner, without fail. Lettuce from the garden when she had it, from the market when she didn't. Onion sliced so thin you could read through it. Azeite from the cooperative in Moura. Red wine vinegar from the barrel in the cellar. Salt. Nothing else.

I've watched tourists in Lisbon look confused when this arrives at their table. Where's the dressing? Where are the toppings? They don't understand that this is the dressing. This is the salad. The simplicity is the point. When your olive oil is good and your lettuce is fresh, you don't need anything else.

At my Mesa da Avó dinners, I always serve this alongside the main course. People ask for the recipe and I have to explain: there is no recipe. There's just technique. Dry your lettuce. Slice your onion thin. Dress it at the table. Eat it immediately. A cozinha é memória, and this salad is the memory of every Portuguese meal I've ever eaten.