Great Britain's Simon Yates took the overall lead as American Benjamin King produced a second win of the 2018 Vuelta a Espana on stage nine.
Yates finished ninth on a day where an 11-strong breakaway group built a lead before King broke clear to land a win for which he said he "suffered".
The Team Dimension Data rider, 29, beat Trek-Segafredo's Bauke Mollema by 48 seconds on the mountain finish.
BMC Racing's Dylan Teuns was third, two minutes and 38 seconds behind King.
'I've never suffered like that'
King sat exhausted after his gutsy win on the 200.8km mountain stage from Talavera de la Reina to La Covatilla, where the closing 20km contains gradients of up to 16.4%.
The Virginia-born rider had never won a Grand Tour stage going into the Vuelta but now has two victories having also won stage four, the only other mountain stage to date.
He timed his push expertly, with 19km remaining he broke away from a group which had built a lead of over nine minutes on the peloton with 32km to go.
"To get one win was a dream come true," said King, who raced for five hours 30 minutes and 38 seconds. "I worked hard for it and made wining a Grand Tour stage a major career goal.
"So today was really nice to show it wasn't a random thing that first one. The team and I prepared for opportunities like this. I've never suffered like that in my life on the last climb but I'm sure it will settle in now. It's a real honour.
"There are more break-away days coming up I think so I'll keep looking for opportunities."
Mitchelton-Scott rider Yates was two minutes and 49 seconds down on King but now has the general classification lead, albeit just a second ahead of Spaniard Alejandro Valverde and 14 clear of Nairo Quintana.
Yates, 26, finished sixth overall at the Vuelta in 2016 and led the Giro d'Italia in May for 13 stages before fading on stage 19 when eventual winner Chris Froome launched a stunning solo attack.
Colombian Quintana won his second Grand Tour at the Vuelta in 2016, while his Movistar team-mate Valverde, 38, won the 2009 edition.
Previous race leader Rudy Molard was dropped early on the final climb, while Team Sky's Michal Kwiatkowski lost a further minute to drop out of the top 10.
Monday will be the Vuelta's first rest day, with stage 10 of 21 coming on Tuesday - a flat stage from Salamanca to Fermoselle.
Stage nine result
1. Benjamin King (USA/Dimension Data) 5hrs 30mins 38secs
2. Bauke Mollema (Ned/Trek-Segafredo) +48secs
3. Dylan Teuns (Bel/BMC) +2:38
4. Miguel Angel Lopez (Col/Astana Pro) +2:40
5. Nairo Quintana (Col/Movistar) Same time
1. Simon Yates (GB/Mitchelton-Scott) 36hrs 54mins 52secs
2. Alejandro Valverde (Spa/Movistar) +1sec
3. Nairo Quintana (Col/Movistar) +14secs
4. Emanuel Buchmann (Ger/Bora) +16secs
5. Ion Izagirre (Spa/Bahrain-Merida) +17secs