When blu opened at Sports Club/LA last winter, many eyed the restaurant with suspicion. Would the brightly colored, Cali-inspired glass-walled dining room work in Boston? Would the menu be filled with bland, flavorless health club fare? The answers: yes and no—in that order. And it’s all thanks to Dante deMagistris, the 27-year-old Belmont native who has won the hearts and stomachs of Bostonians with his culinary style (honed under Michael Schlow during their stint together at Café Louis and flourishing under blu co-owner and culinary legend Michela Larson). Even fitness-phobes clamor over deMagistris’s fresh seasonal dishes. His “Out of the blu” appetizer, a presentation of assorted sashimis served on brightly colored glass plates, is a work of art, while entrées like steamed wild striped bass or potato gnocchi (made from deMagistris’s grandmother’s recipe) show the promise of a chef on the rise.