Pork Tenderloin with Mustard Sauce

I've had this recipe from allrecipes.com saved for weeks, and I finally got around to cooking it. We really enjoyed it. The mustard sauce goes a long way, so next time I'll probably reduce the amount I make. The pork was very tender, and the sauce was the perfect pairing.

Ingredients:
1/3 cup red wine
1/3 cup soy sauce
2 tablespoons light brown sugar
2 pounds pork tenderloin
1/3 cup mayonnaise
1/3 cup sour cream
1 1/2 tablespoons mustard powder
1 tablespoon minced fresh chives (I used green onions)

Directions:
Combine wine, soy sauce, and brown sugar in a large resealable plastic bag. Place tenderloin in bag, and refrigerate overnight, or at least 8 hours.
In a small bowl, combine mayonnaise, sour cream, mustard powder; mix well. Mix in minced chives if you wish. Chill until ready to serve.
Preheat oven to 325 degrees F. Place meat and marinade in a shallow baking dish, and roast for 1 hour, basting occasionally. Temperature of meat should register 160 degrees F. Let rest for a few minutes, then cut into 1/2 inch thick slices. Serve with mustard sauce.

My note: The sauce is best if made several hours, or even a day in advance, to let the flavors blend well. You may need to adjust the amount of dry mustard to suit your taste - best to start with less, and add more if needed.