Combine first 5 ingredients for pico de gallo; set aside.
Meanwhile spray large skillet with cooking spray. Add cactus paddles, in batches; cook on high heat 5 min. on each side or until cactus is lightly cooked and sticky liquid has evaporated.
Top 6 cactus paddles in skillet evenly with chorizo and Singles; cover with remaining cactus paddles. Cook 3 min. or until Singles are melted. Serve with pico de gallo.