Also, what’s your workspace? It helps if you work in a separate room with a door. Working in a central open spot like the kitchen table invites more interruption. Of course this is hard to do if you’re in a small apartment.
Some people who we love deeply, just cannot do this. If we're physically there, a reason to interrupt will always be found. IMHO it's not worth damaging the relationship.
I don’t want to read too deeply into your comments, but it may be worth exploring why expressing this need feels like it would damage your relationship. It could be that you both need to adjust your communication patterns to better express yourselves and hear each other.
Also, what’s your workspace? It helps if you work in a separate room with a door. Working in a central open spot like the kitchen table invites more interruption. Of course this is hard to do if you’re in a small apartment.