I accidentally baked frozen dairy bourekas (not liquidy) on parchment paper on a pareve pan. Does this turn my pareve pan dairy?
You should clean off any residue on the pan, heat up the oven to at least 200-250 degrees Celsius, and put the pan in the oven until the pan heats up to 200-250 degrees Celsius. It can then be used for parve.
All the best
There are two issues.
Firstly, the dairy might have seeped through the parchment paper on to the pan. This issue is actually fairly complicated. Without getting into the specifics, many Poskim write that cheese is considered כחוש (lean) and therefore will not impart taste more than a קליפה (Shulchan Aruch Y:D 94:8, Bais Yosef Y:D end of siman 94 ד”ה כתב רבינו ירוחם, Shach ibid:32, Pri Megadim Sifsei Daas 94:33, Rebbe Akiva Eiger Y:D 105 se’if 4. C.f. Chovos Da’as Y:D 94:17). Therefore the dairy will not impart flavor through the bourekas dough into the pan. However, some contemporary Poskim say that our cheese is different than the cheese discussed by the Poskim, and our cheese might be considered דבר שמן (fatty). Of course, if the dairy itself seeped through the parchment paper onto the pan, the pan would be dairy.
Secondly, there is the issue of זיעה, i.e. taste imparted through halachic steam. Regarding the issue of זיעה- steam- there are reasons to be lenient altogether and not require kashering the pan. The reasons being that the bourekas are dry (see Pischai Teshuva Y:D 92:6), and additionally there are opinions that say that an oven does not produce halachic זיעה (steam). However, since there are those who are stringent, and it is fairly easy to kasher the pan, one should ideally do as written above, even if none of the dairy seeped through on to the pan.