is the 1529 portrait, when he was around 45, double portrait with Ms. Bore, by Cranach the elder.
This is another Cranach, from 1520. A bit thinner, but still no looker.
Cranach's 1529 became something of an icon and he painted dozens and dozens of copies, which were turned into bad woodcuts.
He was noted as the best early 16th c. painter at "getting a likeness", so that's probably pretty much what Martin Luther looked like.