To make the jalapeño buttermilk, add all the ingredients to a food processor/blender and blend until smooth. Pour half of it into a zip lock bag and refrigerate the other half for serving.
Transfer the ribeye steaks to the zip lock bag with the jalapeño buttermilk and turn to coat. Place in the refrigerator for at least 1 hour to marinate, the longer the better.
Grill the ribeye steaks on a hot fire or griddle pan, turning to cook on both sides to your preferred doneness (see cooking guideline above).
Transfer the meat to a board and allow to rest for half its cooking time.
Slice the beef and season with salt and freshly ground black pepper.
Serve these tender ribeye steaks with the remaining jalapeño buttermilk and sides of your choice.