Drain the tuna well and put it in a bowl. Break it up loosely with a fork.
Halve the avocados, remove the stones and scoop out the flesh. Add it to the tuna in the bowl.
Add the lemon juice and roughly mash everything with a fork. The cream can still have a little texture.
Finely dice the onion and fold it into the tuna and avocado mixture. Season with salt and pepper.
Wash the lettuce thoroughly and pick off sturdy leaves. Let them dry well.
Fill the lettuce leaves with the cream and serve the lettuce boats fresh straight away.
Good to know
When it has to be quick, this is the kind of meal that still feels really good. Creamy, fresh and pleasantly light – without much effort.
Swaps
Tuna → tinned wild salmon (also provides plenty of protein and omega-3 fatty acids). Avocado → diced cucumber with 1 tbsp olive oil (fresher, hardly any carbs). Butterhead lettuce → romaine lettuce (usually crunchier and a little sturdier). Onion → spring onion (milder in flavour).
Allergens
Contains fish; for children, only serve it finely chopped and mildly seasoned, and during pregnancy use tuna that is well cooked or safely preserved, and watch the amount because of possible mercury.