Is there a way to burn a Lion installation DVD-R from a new Mac mini or Macbook Pro? I got a new Mac mini and Macbook Pro, and hope to burn a Lion installation DVD-R if it needs to be used in the future.

But I searched for any file greater than 1GB on the hard drive and didn't find any.  Since we can use command r to boot up a partition for reinstallation, is there a way to mount that partition and burn the image to a DVD-R?
You can easily create a bootable USB drive as long as it's at least 1gb by using Apple's Recovery Disk Assistant. This will create a recovery partition on the drive but still needs to download Lion if you need to reinstall it at a later date.

You can create a bootable image from the original Lion installer download if you kept a copy of it, but you need an 8gb drive, so unless you have dual layer blank DVDs, then this isn't really worth the hassle, and using a spare USB drive would probably be easier. A great guide for doing this can be found here.