This is a fascinating idea, but there's no widely accepted scholarship about a Leonardo being in Burgos cathedral. And if it really was a Leonardo, it would probably be gone because someone would've stolen it!
It's still an incredible place...
en.wikipedia.org
This gorgeous painting does look da Vinci-esque to my eye, but it's unlikely. Really, it would be priceless and it would've been removed and replaced with a copy. There are 24 paintings mostly accepted as Leonardo's. Half a dozen of those are still being argued about. The last Leonardo that came on the market sold for $450 million US. About 400 million Euros. And that one's being argued about.
The painting in Burgos: "The Enigma of the Magdalene."