your burger seasoning.
This may sound silly for a burger, but I always add a bit of Italian seasoning. Not to much or it will overwhelm all other flavors. Just a pinch on each burger, give a nice zest. The only complaint was the time the lid came off.lol. always get asked what I do to my burgers. Now all my friends put it in their burgers too.
If you try it and like it let me know. Or don't like it. Let me know.