Any bike.......The choices are endless then
I would recommend, a medium-to-large capacity upright, naked bike. Very comfortable, very easy to handle, good for commuting and you can add a windscreen later on if you plan on doing more miles. A second hand one obviously is best to start on to see if you like it (and in case you drop it). Go have a look at the CB1300, XJR1300, ZRX1200, GSX1400, (W800 or CB1100 if you like that style), maybe some Triumphs which I don't know much about....I know these engines all seem large, but (except the retros which are pretty slow) they're all incredibly lazy at regular speeds and only really take off when you demand it. They also hold their value well and are incredibly cheap.