Soften stick of butter. Rub loin with butter (you don’t need to use all of it and you may also use unsalted butter to control the amount of salt you are using). Season the loin with garlic powder, salt and pepper. Then rub Worcestershire sauce generously all over the loin.
Broil on each side for 10 minutes. Remove from oven. Let cool, then wrap with plastic wrap and store in the refrigerator (in the entire pan you used).
NEXT DAY:
Bring out loin and let come to room temperature. Cook in the same pan, at 350 for 20-30 minutes (depending on the size of the loin). Take the loin out of the oven. Remove the loin from the pan and set aside. Take 1 Cup water and use some of it to loosen the bits (deglaze) from the pan. Add those drippings to a sauce pan, along with the remainder of the 1 cup of water and the contents of a small bottle of ketchup. Bring to a boil and reduce heat, simmer for 5 minutes. Return the loin to the pan and pour some of the sauce over the loin. Bake for another 10 minutes, or until an instant read thermometer reads between 145-150 degrees (adjust for your personal tastes, more time if you like your meat more on the cooked side). Pour the remaining sauce in a serving dish. Remove your loin and let rest for about 5 minutes before slicing.