Read this article from the Daily Maverick on the tallest buildings in Africa. It seems the Carlton Centre in Johannesburg CBD still holds the title and has has held it since 1973!
Other African countries like Ethiopia and Ghana are vying for the title, but South Africa has a ace up its sleeve in the form of Symbio-City, a planned 447m high building in Centurion, making it, once complete, taller than the Empire State Building in New York ! See the artists impression of Symbio-City below:
Artists impression of Symbio-City in Centurion