Jurors -- who heard recordings during the trial of Viens, 49, telling sheriff's homicide investigators he cooked his wife's body to dispose of it -- returned the guilty verdict after deliberating for about 5 1/2 hours during three days, the Los Angeles Times reported.
Dawn Viens was 39 when she was last seen in October 2009.
David Viens, who pleaded innocent, was hospitalized in 2011 for injuries sustained when he jumped off a cliff after learning he was a suspect. Investigators were questioning him at the hospital when he confessed to killing Dawn Viens after a fight and cooking her body -- but his attorney, Fred McCurry, says police lacked physical evidence to support a first-degree murder prosecution.
David Viens was heard on audiotape saying he put his wife's body in a drum of boiling water and weighed it down to keep it submerged.
"I just slowly cooked it and I ended up cooking her for four days," he told investigators, although it wasn't clear where it occurred.
He said he mixed some of her remains with waste and poured it into the grease pit at his restaurant and put other remains in garbage bags and threw them into a trash bin.