Not very, reader Sue, which is why we can say definitively who invented it: one Alexandre Micka. Micka was born in Poland, though his family emigrated to the Lorraine region in extreme northeastern France when he was but a lad, about 1915. It was there that Micka worked as an apprentice pastry maker. For exactly how long is unknown, or at least it is unknown to me.
What’s clear is that in time Micka relocated to St.-Tropez, probably about the year 1950, and opened his own pastry shop. He created Tarte Tropézienne soon after and sold it with only modest success. That is, up until the 1960’s when St.-Tropez caught on as a tourist destination and visitors began enjoying what they thought was an indigenous delicacy. Tarte Tropézienne has been famous ever since.