At 51 Lincoln, a fruity summertime staple is cooked to look just like another warm-weather favorite. Watermelon “steak” salad ($11) is a mainstay at Jeff Fournier’s upbeat neighborhood joint, where his own paintings adorn the walls. He bakes seedless watermelon in butter and sherry, dusts it with coriander and fennel, then sears it on high heat. The result is a charred, almost meaty melon. He serves it with golden beets, French feta, red-beet vinaigrette, and fresh herbs — plucked straight from his rooftop garden.