Here’s the best info I could come up with.
I do not have the exact answer but as far as I know, only two countries have had an elected ethnic minority national leader at some point in history: Peru (Fujimori) and Fiji (Chaudhry)**. India (Singh) and Bolivia (Morales) could be considered but I am not sure if either count as a true elected ethnic minority leader, Singh was not elected and is more part of a religious minority. Morales is part of the indigenous population but technically, indigenous groups are the majority even though they are very rarely in power.
Source
Personally, I was surprised to not see South Africa mentioned, but those leaders were not elected either.