I just used the first four ingredients to marinate boneless chicken breasts (for about 3-4 hours) and then we grilled them outside. Very tasty and very easy. The chicken was moist and had a nice zip. I usually don't have buttermilk in the house and while looking for an ingredient for another recipe, I discovered "saco cultured buttermilk blend" in the baking aisle. It's a powder you reconstitute to make buttermilk as needed and it worked beautifully. Also, only has three ingredients--"sweet cream churned buttermilk, seet dairy whey and lactic acid."
This was so good - my family loved it. The gochujang has such a great flavor and spicy kick. The buttermilk makes it so tender and the lemon adds a really nice brightness. Also, it couldn't be easier. We only let it marinate for about 45 minutes and it still infused a ton of flavor. Will definitely make again, next time letting it marinate for a full 3 hours.