Thymen Arensman rode away from the remains of a breakaway to win on the tough climb up the Sierra Nevada on Sunday while Remco Evenepoel lost more of his Vuelta lead.
Evenepoel, who cracked at the end of Saturday's stage losing 52 seconds of his advantage, again could not keep up with his main rivals at the end of the final climb.
The Belgian still took heart from losing only 15 seconds to second-place Slovenian Primoz Roglic on 152.6km stage 15 which ended at 2,513m, the highest altitude of the Vuelta.
"Really happy! I lost almost nothing." said Evenepoel who rides for Quick Step.
He added that Saturday had been a bad day but "today was better".
Arensman, a 22-year-old Dutchman with DSM, was part of a large breakaway which splintered on the final climb.
"I can't believe it, the Queen stage on the Vuelta," said Arensman, at 1.90m unusually tall for a climber. "Sierra Nevada on altitude. Everyone was talking about this stage."
"I didn't feel super-good on this stage but apparently the others felt their legs even more."
Spanish veteran Marc Soler, who had climbed to victory in stage five, pulled away early on the 22-kilometre final climb but Arensman gave chase as the slope steepened and then surged away.
"It looked like he was waiting for me," said Arensman. "I was thinking 'Marc Soler, he's such a great rider I don't know if I can take him on.'
"But then I accelerated on the steepest part and he cracked. And I was like 'everyone is really on the limit and I maybe have something left'."
Down the mountain, Spaniard Enric Mas of Movistar, in third place, also had something left.
He escaped from the elite group first and pulled away to finish second 1min 32sec behind the winner. Mas gained 32 seconds, with bonuses included, on Evenepoel.
Second-placed Roglic of Jumbo sat on Evenepoel's wheel up most of the final mountain before attacking late, quickly dropping Evenepoel and gaining 15 seconds.
Evenepoel's lead shrunk to 1min 34sec over three-time defending champion Roglic with Mas at 2.01.
Nevertheless, the 22-year-old Quick Step rider, who, like Arensman, grew up at sea level in the Low Countries, took heart from the way he had limited his losses at altitude.
"My first time finishing so high so I think I did quite well," he told broadcaster Eurosport while pedalling a stationary bike and chugging a can of soda.
"I had to do the whole climb then Primoz attacked with 2k to go. It's in his right, but I managed very well."
Evenepoel fell on stage 12 on Thursday.
"I still felt a bit the stiff muscles from the crash but its getting better every day," he said. "Really happy it's a rest day tomorrow."
After the rest day, the riders take to the road again with a flat stage on Tuesday, there is some climbing on Wednesday before the peloton returns to the mountains.
Evenepoel said the hardest part was over.
"Now the third week is here, a bit of another story, the climbs are not super-super-hard anymore," he said