You can find Tonnino tuna some specialty and health foods markets, or visit http://www.tonnino.com.
- Place the romaine in a large serving bowl.
- Arrange the tomatoes and cucumbers around the sides, top with tuna filets.
- Drizzle with 2 Tbs. of olive oil from the tuna jar and lemon juice.
- Add salt and pepper to taste, garnish with feta if using, and serve.