Remove and discard leg truss from turkey. Pull off and discard any lumps of fat.
Remove giblets and neck (they're often packed in neck or body cavity) and save for classic gravy. Rinse turkey inside and out; pat dry. Rub turkey all over with butter.
Place turkey, breast up, on a V-shaped rack in a 12- by 17-inch roasting pan (or one that is at least 2 in. longer and wider than the bird). Insert a meat thermometer straight down through thickest part of breast to the bone. (If using an instant-read thermometer, insert when checking temperature.)
Roast in a regular or convection oven until thermometer registers 16
(See below for times and temperatures.)
If turkey is unstuffed, tip slightly to drain juices from body cavity into pan.
Transfer turkey to a platter.
Let stand in a warm place, uncovered, for 20 to 30 minutes, then carve. If thigh joints are still pink (common in an oven-roasted bird), cut drumsticks from thighs, place thighs in a baking pan, and bake in a 450 oven until no longer pink, 10 to 15 minutes, or put on a microwave-safe plate and cook in a microwave oven at full power (100%) for 1 to 3 minutes.
