The purpose of this study is to test a novel, cognitive behavioral treatment strategy to improve social functioning in adults with autism spectrum disorder. The treatment, named TUNE In (Training to Understand and Navigate Emotions and Interactions), includes components to address the many behavioral domains involved in social functioning, including social motivation, social anxiety, social cognition, social skills, and generalization of the skills to community settings. The Investigators will test the efficacy of TUNE In to improve social functioning in adults with autism spectrum disorder (ASD), using a randomized controlled trial using the SRS-2 as the primary outcome measure.