Step 1Season the tuna liberally with salt and pepper. Put the bay leaves, peppercorns, chiles and the zest of one lemon in a saucepan, and place the tuna on top.
Step 2Cover the tuna with 2 cups of the olive oil and heat over the lowest possible heat until the tuna begins to turn opaque and small bubbles just start to form on the surface, about 30 to 35 minutes. Remove from the heat and cool to room temperature. The tuna prepared to this point can be stored for several days in the refrigerator.
Step 3Remove the tuna confit from the oil (you can reserve oil for the next time you make tuna confit). Flake the tuna into a bowl. Add the beans, red onion, parsley and the remaining lemon zest, and toss lightly. Add the remaining olive oil, juice of the lemon, and salt and pepper to taste.