Samin Nosrat of Salt Fat Acid Heat (popular Netflix series) talks of how she buttermilk marinades a chicken. In short, take your washed, defrosted, whole chicken and place it in a large reuseable Ziploc freezer bag. Mix 2 tbsp salt into 2 cups of buttermilk. Pour the buttermilk mixture into the bag with the chicken in it. Seal it and place on a plate in the fridge.
If you remember, turn the chicken over during the marinating time. Ideally this is 24 hours but half a day or a few hours will work too.
As Samin so carefully explains, the buttermilk and the salt work like a brine to tenderize the meat. While cooking, the sugars in the buttermilk caramelize and turn the skin golden brown.
To cook, remove the chicken from the Ziploc bag and bring to room temperature. Scrape off as much buttermilk as you can and roast in the oven. Remember to rest the chicken for 10 minutes before serving.
View the full recipe on the Salt Fat Acid Heat website.