The grilled yellowfin tuna sandwich ($8.75) at Becks Prime (2902 Kirby, 713-524-7085 and other locations) is an excellent choice for several reasons. Their supplier line-catches the fish by hand, as opposed to using nets and possibly endangering other marine wildlife. The three-quarter-inch-thick tuna steak is mesquite-grilled to a medium-rare finish, leaving the steak purple on the inside. It's served with sprinkles of feta cheese, slices of cucumber, tomato and red onions, and a sesame-seed-covered egg bun in a light coating of a wasabi-ginger spread. Since yellowfin tuna has been recognized as a source of omega-3 fatty acids, you have another reason to feel good about what you're eating.