Hi Joe, yes, you can start with simply removing the excess foliage "outside of the dome" now. That's not a bad way of putting it! Basically, you will just be doing topiary trimming for now. Then let's see how the tree respond. It should be very satisfying to see the tree push back with new growth. Don't forget to fertilise it in a few weeks. It is good to start out with organic fertilisers and stay away from chemical fertilisers for potted trees. Chemical fertilisers are only good for plants that are in the ground. In the future, you can consider other options, like growing it out in the ground for faster development, or you can even cut it back really hard (not recommended right now).
Good luck with it!
Si