"Masterchef" 8 p.m. Fox — The Top 6 contestants are tasked to take over a high-end restaurant in Los Angeles."The Unauthorized Saved By the Bell Story" 9 p.m. Lifetime — How much of this is true? Only Dustin Diamond, who oversaw this project, knows for sure."Dallas" 9 p.m. TNT — Elena confronts the Ewings in an all-out showdown."Under the Dome" 10 p.m. CBS — Big Jim learns the shocking truth about what really happened to his wife, Pauline."Mistresses" 10:01 p.m. ABC (second season finale) — Joss plans her engagement party as Scott arranges another surprise for her.