From Longman Dictionary of Contemporary Englishdrylydry‧ly, drily /ˈdraɪli/ adverb EMOTIONALif you say something dryly, you say something that is amusing but you appear to be completely serious ‘I hear you’re a hero, ’ Philip said dryly.
Examples from the Corpus
dryly• "If you're lucky, " said Harrison dryly, "they'll only hang you."• Theo answered dryly to the effect that it was not so wonderful for his finances.• I must apologise for returning somewhat dryly to the procedural point that has been raised during the debate. 