It wasn’t named after the opera, but given all the soaring notes on the menu, Tosca could have been. Ribbons of carrot-colored pappardelle scattered with thyme-scented rabbit ragu are a light and delicate score; scarlet lamb on a bed of juicy little tomatoes and blac k-eyed peas trace not to the American South but to chef Massimo Fabbri’s childhood in Tuscany; and impossible-sounding combinations -- Gorgonzola and ice cream -- make beautiful music together atop a dessert of shaved pear. Fabbri just turned 29, but (give or take a merely pleasant dish) he’s cooking possibly the best Italian food in the city. Engaging compositions aren’t the only lure. The room, whose design incorporates the colors of stone and champagne, is cool and elegant, and the servers in their formal jackets go about their duties with flair. You don’t need to be a lottery winner to sample the riches. Tosca’s three-course, $35 “Dine at Dusk” deal, served nightly from 5:30 to 7, is a perfect opportunity to spoon into one of the best risottos around.