Funnily enough I took a photo in early June of the exact same plant as you can see by the background rocks.
The second photo is a close-up of the flower and with the orange anthers and the height nearly 2 m, I had concluded that it was probably Reseda suffruticosa. Either way according to "Flowers of Southwest Europe" by Polunin and Smythies, it would seem that it would be rare in the Picos as northern Spain is not indicated as a location.
Reseda alba, Portugal and Med. region.
Reseda suffruticosa, North Portugal, South, South Central and East Spain.