The Teatro Dom Pedro V is a gem. Built in 1860, it both looks like and is a traditional theatre, with gold-fluted columns, plaster molding and orchestra pit. It is, for better or worse (and in many ways better), small with fewer than 300 seats. One can hardly think of a more idyllic place in which to perform opera, yet this Easter weekend production of an opera buffa double bill was the first there in several years.