This is one of the many cake recipes from a small book which I purchased when I visited Wales for the first time. About this cake, it says:
Llanddarog is a village in Dyfed, in contemporary terms on the main Swansea-Carmarthen road. More significantly, and to explain these cakes, it lay on one of the old drovers' routes. They were made with beer, which helped to keep them in good condition for a long while, thus they were popular with the drovers for their long journeys to the English grazing lands. They were about 6'' long, 3 in wide, 1/4 in thick, and cost 2d each.
The recipe says "Bake in a moderate oven" which means 320-370 F. I suggest 350, but it might depend on your oven - if your oven bakes hotter generally, maybe better try 320 F.