Having significant, meaningful research in any field is far better than "checking the box" type research in your residency-specific field.
For research to be advantagous to your application you really need to show that you can plan, conduct, analyze and write up a research project. First-author manuscripts in any field put you head and shoulders over 99% of applicants. Nobody expects you to be innovating the field you are applying too, showing a dedication to academic medicine is enough (obviously though it is even better if your publication is in the field you are applying too, not as much as you might think though.)
Case reports, posters, presentations etc. are nice, but they really just serve to show your interest in a field, they are not in the same league as a first author manuscript.