North End restaurateurs still have a beef — or Bolognese — with the city’s “unconstitutional” $7,500 outdoor dining fee, as four Italian restaurant owners filed a $1.5 million lawsuit against Mayor Michelle Wu on Monday.

The city for the first time this year handed down a North End-only $7,500 fee in response to local residents complaining about the outdoor dining noise and clutter. As a result, a group of restaurant owners began protesting the mayor, and promising this lawsuit against her.