The Grillhouse in Rosebank has been the definitive Johannesburg steakhouse since 1993. South African beef — particularly the aged cuts from the highveld — is genuinely excellent, and the Grillhouse treats it properly: aged on the bone, cooked over coals, served with proper chips and a sauce if you want one. The wine list is long and South African, the portions are substantial, and the room is noisy and satisfying in the way a good steakhouse should be.
This is not a fancy restaurant, but it is exactly what it sets out to be. If you eat one dinner in Johannesburg and you eat meat, this is the classic choice. Book ahead for weekends — it fills up. It is in The Zone @ Rosebank, easy to reach from the Rosebank Gautrain station.