Paul Wilson, 38, suffered a severe anaphylactic shock in 2014 after eating a takeaway containing peanuts from the Indian Garden in North Yorkshire.
The court of appeal heard how owner Zaman was found guilty in a landmark trial in May last year at Teesside Crown Court of the manslaughter and six charges of contravening various food safety requirements.
He denied responsibility but the court had heard how he had cut corners by substituting almond powder and using cheaper ingredients containing peanuts.
But the Court of Appeal in London ruled his conviction was safe and also rejected a bid by Zaman, of Aylesham Court, to have his sentence cut.
Lawyers argued the jury was misdirected during the judge’s summing up of the case.
However, dismissing the appeal, Lord Justice Hickinbottom, who sat with Mr Justice Openshaw and Judge Michael Topolski QC , said: “The case against Zaman was powerful. We consider it to have been overwhelming.
“We are in no doubt that the conviction was and is safe.”
He said the father-of-four was responsible for negligent behaviour that “persisted over months”.
“In our view, his negligence in this case was not just gross, his behaviour, driven by money, was appalling.”
Mr Wilson, a bar manager, from Helperby, had specifically informed staff at the eatery in Easingwold that his meal must not contain any nuts, and the court heard that his allergy was so severe it could be triggered by him being in close proximity to a peanut.
Zaman had cut corners by using cheaper ingredients containing peanuts and he tried to save money because his business had debts of £300,000.
A week before Mr Wilson’s death, trading standards warned staff at the restaurant they had to tell customers their meals contained peanuts after a different customer suffered an allergic reaction at another of Zaman’s restaurants.
Zaman was found guilty of manslaughter by gross negligence and six food safety offences, but was cleared of a charge of perverting the course of justice.