The Health Nazis and the vegan terrorists and etc will tell you that butter is bad bad bad and, maybe, if you're eating it all day, every day, it is. Butter, however, is an essential ingredient. Sometimes you can't do without butter. Sometimes you can but the substitutes are inferior. Sometimes you just have to live a little. I mean, how often, really, do you eat scrambled eggs? Or steak? Or proper mashed potato?
Anyway, Anthony Bourdain, I think it was, introduced me to this simple technique and I've been using it frequently. He (or whoever) says that the what a lot of steak houses do is, when they carve their steaks (after cooking and the critical resting), brush them with a little bit of melted butter. Note this bit: little bit. You're not buttering a fucking dinner roll. You're taking melted butter and using a pastry brush or basting brush to give a chunk of meat a sheen. I've never tried it, but there's nothing at all stopping you from trying this with other meats or cuts, such as roasting joints.
You could obviously use flavoured butter in place of regular butter. By all means experiment with garlic butter, herb butter, red wine butter or whatever you have kicking about the place. Peanut butter, probably, wouldn't be so nice.