Best Beef Tenderloin

I made this tenderloin recipe last weekend. It was a huge hit! My granddaughter, Penelope, asked for seconds. So easy and almost foolproof.

1 (3 - 4 pound) beef tenderloin
1/2 cup chopped onion
1 1/2 T butter melted
1 cup dry sherry
3 T soy sauce
2 t dry mustard
1/8 t salt
1/8 t pepper

Place meat in large shallow baking pan. Bake in a 400 degree oven for 10 minutes

In a saucepan saute the onion in butter until tender. Add the remaining ingredients and bring to a boil. Pour the mixture over the tenderloin. Reduce the oven temp to 325 degrees and bake for 35 minutes or until a meat thermometer reaches 150 to 170 degrees. Baste often with the drippings.