For those who can't read any Russian, or never read that short story where this is the punchline essentially, pectopah is pronounced restoran. It only drops the T, basically.
The reason it drops the T is that the word came to Russian from French (as did so many other words). And the French word "restaurant" is pronounced with a silent 't' at the end, in the typical French way. So the cyrillic rendering of that sound ends up without a 'т' on the end.
That's Cyrillic alphabet, not Russian. Cyrillic is used in other languages as well. I was born in Serbia (which also uses Cyrillic) so I understood the punchline, even though I would hardly say I "read any Russian". It's more of a south and east Slavic thing than it is a Russian thing.