2 lbs Beef Tenderloin
2 teaspoons Salt
1 teaspoon Pepper
1 Red Onion
2 Sticks (16tbl) Salted Butter
8 tablespoon Flour
4 cups Beef Broth
4 teaspoons Dion Mustard
1 medium container Sour Cream

Spread beef on brown paper and season with salt and pepper. Top with onion slices and cover for 2 hours at room temp. Melt 2 tbl butter in skillet, and blend flour, mix with stock and heat. Stir until thickened. Blend in mustard, and remove sauce from heat. Brown beef in other skillet about 10 mins, add beef to sauce. (leaving onions). Simmer for 15 min. Remove from heat stir in sour cream and serve.