There are bigger cuts of beef, but none feeds so many people so quickly. Nick Fauchald serves sliced tenderloin alongside grilled bread smeared with chile butter.
Set up a grill for indirect grilling, with the coals on one side, and heat to 450°. In a bowl, mix the butter, shallots, jalapeńos and chile powder; season with salt. Transfer to a sheet of plastic wrap and roll into a 1 1/2-inch-thick log; refrigerate for 15 minutes.
In a bowl, mix the brown sugar, paprika, pepper and 1 tablespoon of salt. Rub the beef with the spice mixture. Oil the grate and grill the beef directly over the coals, turning, until charred, 12 minutes.
Move the beef away from the coals. Cover and grill for 25 minutes, or until an instant-read thermometer inserted in the thickest part of the beef registers 130°. Transfer to a carving board; let rest for 10 minutes.
Grill the bread directly over the coals until toasted. Spread the bread with half of the ancho-jalapeńo butter. Slice the remaining butter and transfer to a plate.
Slice the beef and serve with the toasts and ancho-jalapeńo butter.