I feel you - I've always had a blackspot in my brain for names; I once was showing a new hire around, and about halfway through introducing my colleagues, my brain gave up and I couldn't remember anyone any more. Just awful.
Extend hand for a handshake. Hey, I'm [name]. We've met before but it's been a while.
First, it lets the other person off the hook, because they're almost certainly experiencing the same momentary anxiousness. Second, literally every time I've done this, they've replied like "Hi, nice to talk to you again! And I'm [name]."