On July 17 last year, the owner of Grey Lynn's ohSO Cafe was driving on St Marks Rd in Newmarket when a man changed lanes in front of him, causing him to "become very angry", according to court documents.
He followed the driver to Remuera Rd where both men got out of their cars and fought.
"The defendant proceeded to hit the victim in the head with a steel tyre iron, causing a deep laceration to the chin of the victim requiring stitches," court documents said.
Zajmi put the implement in a second vehicle being driven by his wife and it was never found.
He told police at the time he had only punched the man but later pleaded guilty to the police's summary.
Zajmi and his wife bought their trendy central cafe in 2013 and another one at NorthWest Shopping Centre eight months ago.