I could also picture them spreading some moretum (crushed cheese with herbs and olive oil, it’s rather tasty) over the dough. The white thing in the afresco is certainly not moretum as the later is green, but frankly that doesn’t sound too far from what I’ve seen people adding to pizza bianca.
Likely not used on pizza though, I’d imagine. But a cheese like feta, which would have been more common, would probably still taste great.
I could also picture them spreading some moretum (crushed cheese with herbs and olive oil, it’s rather tasty) over the dough. The white thing in the afresco is certainly not moretum as the later is green, but frankly that doesn’t sound too far from what I’ve seen people adding to pizza bianca.