Return Dutch oven to medium heat. Add quinoa and salt; cook over medium heat 1 to 2 minutes, stirring occasionally, until fragrant. Slowly stir in broth. Stir in beef mixture. Heat to simmering over high heat, stirring occasionally. Cover; reduce heat to medium-low. Cook 23 to 27 minutes or until liquid is absorbed and quinoa is tender. Stir in spinach.