Step 1 Beat the butter, rosemary, salt and lemon zest until creamy. Spoon the butter onto a sheet of plastic wrap in the shape of a log and roll it into a cylinder. Twist the ends of the plastic wrap in opposite directions to firm the cylinder and roll it gently on the counter to eliminate any air pockets in the center. Refrigerate until ready to use. This makes about ½ cup rosemary butter, more than is needed for the rest of the recipe; the butter will keep, covered and chilled, up to 2 days.