The very best steaks gain much of their richness from what's called "marbling," thin seams of fat that streak the muscle tissue. If you're working with beef that isn't as richly marbled as you'd like, you can rub or brush your steaks with butter before they go on the grill. Your best option, for several reasons, is to melt your butter and apply it with a brush.
The Microwave Is Your Friend
The butter in your fridge is up to 20 percent water by weight, and water is a bad thing when you're grilling. It turns to steam on the grill and slows the browning of your steak. Circumvent this by putting your butter in a narrow measuring cup and melting it in the microwave. Its water will sink to the bottom, leaving pure or "clarified" butter floating on top. Clarified butter withstands the grill's high heat without burning, lending your steaks a rich flavor and helping them form a perfectly browned crust.
A Bit of Finesse
For added panache, melt your butter a day ahead of time and season it with garlic, spices or fresh herbs. Those flavors will infuse the butter and be transferred to your steak the next day when you re-melt it and brush it on.
You'll also have the opportunity to pour the liquids from the solid butterfat before you re-melt it. Steakhouses often finish their steaks with a pat of plain or seasoned whole butter, added just before the hot steak comes to your table. This is optional, but it looks impressive and gives your steaks that little something extra.
Beautiful, buttery steak.