Slice the avocado lengthwise in half and remove the big seed in the middle. Scoop the avocado out of the skins (or peel both halves) and then dice the green avocado flesh roughly into bite-size pieces. Add this together with the finely chopped red onion to a large mixing bowl.

Peel the cucumber. Slice it in half lengthwise using a sharp knife. With a teaspoon remove the seeds in the middle. Then chop up the cucumber and add it to the other vegetables in the mixing bowl.

Rinse the black beans. Flake the canned tuna with a fork. Add both tuna and black beans to the bowl.

Stir well. Then add the lemon zest, the olive oil, the milk and half of the lemon juice. Season with a little pinch of pepper and salt.

Stir the ingredients again. Check the seasoning and add extra lemon juice, pepper or salt to taste if necessary to taste. Sprinkle with the freshly chopped cilantro and mint.

Then give the salad one last good stir. Put it in the fridge and chill it for 20 to 30 minutes. Serve it cold.