Finely chop the parsley and, separately, also the tuna and spring onion.
Remove the fat from the meat. Slice it thinly and arrange it on a large plate.
Season the meat with a little salt and pepper, spread thinly sliced hard-boiled eggs on top, sprinkle with chopped parsley, tuna and spring onion.
Drizzle with oil mixed with a few teaspoons of vinegar.
Stir the dish only at the time of serving.
Notes
For an even lighter variation, substitute olive oil for flaxseed oil and white wine vinegar for apple cider vinegar. These substitutes not only reduce calories but also add an interesting nutritional twist to the recipe.