Perhaps mentioning it as you confirm your pre-order onboard but prepared for what you might get. Asking for a not overcooked item might lead to something very rare.

It is not practical to have passengers make special modifications other than a few things. Sauce on the side, ... You are not dealing with a full kitchen in the sky, or trained chefs (as on SQ). It is principally a "standard" warming-up process for ground-prepared meals.