1) If you think that the language/framework is intimately important to the hiring process (I don't but I'm not judging) then you don't compensate for that. It's an important data point.
2) If you don't think its important, you don't worry about matching "idiomatic" practices. You don't judge on obvious library mismatches, etc. If you don't feel confident doing that. Don't have the challenge interact with any language specific code. Let them do it in any language you feel confident of judging.
1) If you think that the language/framework is intimately important to the hiring process (I don't but I'm not judging) then you don't compensate for that. It's an important data point.
2) If you don't think its important, you don't worry about matching "idiomatic" practices. You don't judge on obvious library mismatches, etc. If you don't feel confident doing that. Don't have the challenge interact with any language specific code. Let them do it in any language you feel confident of judging.