The thing about cooking our fresh produce is that many of our immune aiding nutrients aren't heat stable - your B vitamins, vitamin C & lots of your antioxidants as examples. Minerals on the other hand are usually dandy so zinc, magnesium etc are all OK with a bit of pan action.
Which is why one of the easiest things I get my clients to do is play around with quick herby sauces like this twist on a pesto recipe that I’ve adorned my roasted celeriac steak with. Not only does it bomb your body with Vitamin C but I’ve also turned to raw sauerkraut as my liquid component because we all know good gut health is integral for optimal immunity.
Add the kraut & herbs to a blender & pulse to a fine chop. Then blitz in the walnuts keeping some larger bits for texture.
Serve on slices of celeriac that have been roasted for 10 minutes at 200°C on each side & runny poached eggs with extra kraut if you’re obsessed like me!.