Saying that it is a Peziza is risky since all Peziza have the inside of the bowl coloured in dark yellowish brown down to dark hazelnut. The only species in Peziza to be clear is Peziza Cerea but that on is dirty white cream yellow and the outside is not dusty. I think you should stick to tarzetta, it's the only one that has this pearl white colour. Catinus gets up to 6 cm large and does not allways grows only on bare soil.
For sure, only a true microscopy can give you the final result.
