Angel Hidalgo led by four shots after a 67 in round two of the 2024 acciona Open de España presented by Madrid.
The home hope followed up his opening 65 in similarly impressive style to reach 10 under par and pull clear of a chasing pack headed by England's Joe Dean on six under.
Three-time champion Jon Rahm was in a group of five players a further shot back.
Hidalgo started from the tenth with consecutive birdies and though he gave one back at the 12th - where a trademark booming drive found the right rough - he was back on track with a gain at the 14th.
Further birdies at the second and eighth brought him home in 34 and under par by double figures for the tournament.
Despite just a two-shot difference between his rounds - a remarkable 13 fewer than Rikuya Hoshino, who followed a 77 by going close to the course record with a 62 - and leading both days, Hidalgo said: "Completely different, I would say.
"I already said to my caddie, I feel every shot today. Yesterday, I was completely blind and I was just hitting the ball and I don't know why it was directly to the pin.
"But today I played really good. Two bad drivers to finish the round on four and seven, probably the birdie chances from the back nine for me today, but really happy with the way I play."
Dean enjoyed two eagles, including a chip-in at the fourth, in an impressive round of 65.
After also making five birdies and three bogeys, he said: "It's been great, felt a little scrappy in places but overall a great day.
"Par-fives have been very good to me, just some delicate hands the last two days. I think I rubbed some 'Spanish hands' off on me. Great chip-in."
Rahm also eagled the fourth, helping him to a two-under-par 69 that also included four birdies and four bogeys.
He said: "It's a little frustrating after such good work yesterday in the heavy winds to not take advantage of the easier conditions today - especially my first 11 holes, barely any wind.
"Everything just felt one or two levels below what I would have liked to feel. There's a couple of moments, making that eagle putt was something that kind of renewed the energy in me, but just a few too many mistakes."
He was alongside compatriot Alfredo Garcia-Heredia, Frenchman Julien Guerrier, England's Sam Bairstow and United States Ryder Cup star Patrick Reed on five under.
Two more Spaniards, Adri Arnaus and David Puig, were at four under alongside England's Tommy Fleetwood and American Jimmy Walker.
Fleetwood was desperately unlucky at the ninth, his tee shot hitting the base of the pin on the full only to ricochet more than 50 feet away - from where he three-putted for bogey.
He made just one birdie and one bogey the rest of the way and said: "Started off really well and just turned out to be a bit frustrating. Bad break on nine, if you like.
"It's not the worst position to be in but after such a hot start, felt like I was playing well, a bit frustrating to not shoot a better score. But that's golf."
Spanish amateur Luis Masaveu made the cut at two under while the round of the day belonged to Japan's Hoshino, with 10 birdies - including six in a row from the 14th to the second holes, and another run of three before a closing bogey at the ninth.
Jens Fahrbring provided another of the highlights of the day, a hole in one at the 208-yard 11th hole helping the Swede to one under par for his round and the tournament.
