The 27-year-old, who capped five times by Ghana was sent off late in the first half of the Eternal derby as matches between the Balkan country's two most popular clubs are known.
"... and for the Levski Sofia fans: keep making those monkey sounds! It makes me feel sooooo strong and proud of where I come from," the CSKA winger wrote on Instagram.
Levski denied any wrongdoing. "I was at the match and I haven't heard any monkey noises," a Levski spokesman said. "We're not planning to issue a statement at this stage."
Levski, 26-times Bulgarian champions, have been fined several times in recent years by European soccer's governing body UEFA and the Bulgarian Football Union for racist incidents.
Sunday's Sofia derby was marred by crowd trouble and police detained 44 people for public order offences.