Slightly warm the beans—they should be warm, not hot.
Combine them with the tomatoes, cucumber, onion, basil, and capers.
Add the tuna in large pieces, then dress with lemon, vinegar, olive oil, salt, and plenty of pepper.
Toss gently so the tuna doesn’t turn to mush.
Tucci’s key move is adding the beans while they’re still slightly warm, which helps them absorb the dressing and gently brings out the other flavors.
Also, tuna packed in olive oil will taste noticeably better here than water-packed tuna.
