Honestly, have neither of you heard of coderpad? My screens are like the GGP's question, except both I am the candidate are on the phone and on coderpad. Coderpad even had voice and video calls now. The candidate is free to Google, to use the repl, to use any language, etc. If the candidates wants, they can just share their screen in their own environment.
But asking a candidate for 30-50 lines of code is completely normal.