Rinse the farro under running water, then boil it in plenty of salted water for 20–25 minutes (check the package time). Drain and let it cool slightly.
In a pan, warm a drizzle of olive oil with the crushed garlic clove. Add the tomatoes (halved) and sauté over high heat for 4–5 minutes, just to soften them. Season with salt and pepper, then remove the garlic.
Add the flaked tuna and the olives, stirring briefly to warm them through.
Add the farro to the pan and toss everything together, finishing with a drizzle of olive oil.