Winthrop, which neighbors East Boston, has as much of an old-port feel as one will find in the city. Walking over the Winthrop Bridge (which straddles East Boston and Winthrop) a few weeks ago, we came upon Belle Isle. We had heard the place is first-rate, but what impressed us most was its appearance. It’s a shack of the sort you’d find in an Atlantic beach town, with a disproportionately large specials board outside. (The day we stopped in it was swordfish prepared any way.) We got the Cajun tuna (a decision we wondered if we should feel bad about), served with cole slaw, tartar sauce, dinner roll, and rice pilaf that transcended the typical (a light cheese seemed to be the secret ingredient; it’s not pictured here because we’d already devoured it). The place also has raw seafood for the cooking, and we’re hankering to get some on our grills. Or, we might be just as happy to let the cooks at Belle Isle do the work.