According to Nielsen Media Research, Fox News' coverage of the meeting between the United States and North Korea topped cable news, ranking number one across Total Day and Primetime in both total viewers and demos. 

In total day, Fox News was a strong number 1 with MSNBC second and CNN last. Here is the Nielsen numbers:

Total Day
FNC: 2,078,000 in P2+ (466,000 in 25-54)
CNN: 860,000 in P2+ (288,000 in 25-54)
MSNBC: 1,069,000 in P2+ (226,000 in 25-54)

In Prime Time there was a bit of good news for CNN and Chris Cuomo. While miles behind Hannity, Cuomo did climb up into second place in the demos and just barely miised getting to second in total viewers. 

Cable News Ratings:
9-10PM/ET
FNC's Hannity delivered 5,902,000 P2+ and 1,486,000 A25-54
CNN's Cuomo Primetime delivered 2,362,000 P2+ and 904,000 A25-54
MSNBC's Special Coverage delivered 2,378,000 P2+ and 494,000 A25-54

But, the big winner in the coverage was Fox News, which nuked the competition on the nuke talks between Trump and Kim Jong Un.