Friends say the 44-year-old suffered a heart attack in his sleep.
Ruiz owned Marie's Italian Specialties in Chatham for many years and was the executive chef at Sabor in Rutherford, along with Cuban Pete's In Montclair.
Before that, he worked as a sous chef at Dish in Clifton.
Last June, Ruiz opened La Cubana in New York City, paying homage to his Cuban roots.
Food Network star Guy Fieri lamented the loss of his good friend on social media.
"I'm heartbroken that my friend chef Carl Ruiz is gone," the "Diners, Drive-Ins and Dives host wrote.
"I have no words to describe what a great friend he was to me and my family. His ability to make me laugh and smile under any circumstances was only outshined by his talent as a chef.
"Over the years, I’ve met a lot of great people but a friend like Carl is one in a hundred million. Carl ’The Cuban’ Ruiz will forever live on in my heart and in those of all who loved him."
With more than 25 years in the food industry, Ruiz became a familiar face in the New Jersey/NYC dining circuit.
"His frequent appearances on The Food Network — both as a competitive chef champion and celebrity judge — have cemented this Cuban chef sensation as a household name," his website says.
"Whether he is cooking up Cuban delicacies like Fufu or the classic Elena Ruz Sandwich, offering sage advice to up-and-coming chefs, or critiquing show contestants’ finer points of culinary execution, everyone is bound to walk away learning something new."
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