Ryan Henderson's 54th-minute goal was enough to earn Donegal Celtic victory over 10-man Cliftonville in Friday's Irish Cup clash at Suffolk Road.
DC also ended the match with 10 men after Paul Bradley's late dismissal but they held on for a famous win.
Paul McVeigh hit the Reds crossbar early on and the visitors' George McMullan was sent-off on 42 minutes.
Henderson struck the winner after Darren Murray nodded down a Jonny Harkness cross.
McMullan received a straight red card three minutes before the interval after appearing to lunge at Murray with his studs showing.
Bradley received his marching orders two minutes from time after getting his second yellow card.
Reds manager Tommy Breslin opted to leave last weekend's hero at Ballymena Joe Gormley on the bench with Liam Boyce also not earning a start.
Both were introduced in the second half but Cliftonville were unable to fashion an equaliser as DC held on for a notable win over their Belfast rivals.