The 30-year-old joined the Tigers for £3m from Lokomotiv Moscow on transfer deadline day and Bruce said N'Doye's decision to drop his wage demands saw the deal over the line.
"We couldn't have been more delighted with him," Bruce said.
"It was so fraught, we thought we weren't going to get him.
"I've never known anyone take a wage cut as big as he did. It was hundreds of thousands."