The difference between teaching at school and university is that academics are expected to draw on recent & original research for their teaching, and link it to our own research in some way. Teachers aren't.
One hour prep is a bit niggardly - we get 3 for a new module, and while a junior lecturer is new in post and on probation for their first 3 years, they are given a reduced teaching workload, particularly in the first year.
But you work with what you've got ... the first year of teaching in any new post is hectic (I've found that even as a professor - I've got a new core module to teach next year & it'll suck my time).
Be confident that even if some of your lecture topics are not smack bang in your area of expertise, you know FAR more than any undergraduate!
And if you're delivering 1 hour lectures, these are 50 minutes, and if I were you, I wouldn't write the whole text. I use PowerPoint slides to keep me on track, and then speak to them. It's much more effective communication to a large group.
Also draw on all your pedagogical knowledge and break up the hour - give them an activity about 30 minutes in. Also spend the first couple of minutes setting out where the lecture is going to go, and then a couple of minutes at the end to summarise the central points you want them to take away. I tend to assume that an undergrad is capable of maybe 4 to 5 main points of thinking, and the more detailed information around them.
This all feels like spoon-feeding, but in the end I think makes lectures more effective.