Tuna and White Bean Salad with Red Onion, Lemon, and Parsley

General Fast With Fish Published August 02, 2026

Two cans and a lemon. This is the fasting lunch to keep in your head for the days when there is no time and no plan — fifteen minutes, no cooking, and forty grams of protein a serving.

What separates a good version from a sad one is treatment of the onion and the timing of the dressing. Soak the sliced onion in the lemon juice first so it softens and loses its harshness, and dress the beans while everything is at room temperature so they absorb rather than sit in a puddle.

Use oil-packed tuna if you can. On a fish day the oil is permitted anyway, and the texture is better than water-packed by a wide margin.

FASTING LEVEL: Fast With Fish
SERVINGS: 3
TIME: 15 minutes

INGREDIENTS

- 2 x 160g cans good tuna, oil-packed, drained (reserve the oil)
- 2 x 400g cans cannellini or butter beans, drained and rinsed
- 1 small red onion, sliced paper-thin
- Juice of 2 lemons, plus zest of 1
- 4 tablespoons olive oil (or the reserved tuna oil plus olive oil to make up)
- 3 tablespoons red wine vinegar
- 3 garlic cloves, grated
- 1.5 cups (45g) parsley, roughly chopped
- 1/2 cup (15g) mint, torn
- 3 celery stalks, thinly sliced
- 1/2 cup Kalamata olives, torn
- 3 tablespoons capers
- 1 teaspoon dried oregano
- 1/2 teaspoon red pepper flakes
- Salt and plenty of black pepper
- Bread or greens, to serve

METHOD

1. Put the sliced red onion in a large bowl with the lemon juice, vinegar, and a good pinch of salt. Leave 10 minutes — this is the step people skip and it is the one that matters.

2. Whisk the olive oil, grated garlic, oregano, pepper flakes, and lemon zest into the onion and its liquid.

3. Add the drained beans and toss gently. Let them sit 5 minutes to take on the dressing.

4. Add the celery, olives, and capers. Toss.

5. Break the tuna into large flakes and fold it in last, with a light hand. Overworked tuna turns to paste; you want visible chunks.

6. Fold in the parsley and mint.

7. Season aggressively with salt and black pepper, taste, and add more lemon if it is not sharp enough.

8. Serve at room temperature with bread, or piled onto bitter greens.

NOTES

- Canned sardines, mackerel, or salmon all work in place of tuna, and are cheaper and higher in omega-3s.
- Add a diced cucumber and halved cherry tomatoes in summer.
- Better after an hour and still good the next day, though the herbs fade — add fresh parsley when serving leftovers.
- Chickpeas in place of half the white beans give more texture.