The salad-making trucker had stopped for a "rest break" on the M25 near St Albans on Tuesday morning.
He was seen chopping tomatoes and onions on the outside of his lorry, and was told the hard shoulder was "not the best place to prepare dinner".
The healthy HGV driver was fined by police.
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A number of people commented after officers from the Bedfordshire, Cambridgeshire and Hertfordshire road policing unit wrote about the incident on Twitter.
One said: "Truckers get hungry you know," and a number commented on the driver's healthy meal choice.
"You do have to say he eats healthy," another said.
A road policing officer said: "The driver stopped on hard shoulder for rest break and decided to make his lunch on the diesel tank. [He was] issued with a graduated fine."
A lorry driver was spotted preparing his lunch on his vehicle's fuel tank while on the hard shoulder of a motorway.