1 1/2 to 2 pounds top sirloin roast, trimmed
1 teaspoon salt
1 teaspoon ground black pepper
2 tablespoons butter
1 tablespoon olive oil
1 tablespoon flour
1 cup beef broth
1 medium onion, quartered and sliced
3 tablespoons sour cream, room temperature
Cut beef into narrow 2-inch long strips about 1/2-inch thick. Sprinkle meat with salt and pepper and set aside.
Melt 1 tablespoon butter in a medium saucepan. Blend in flour and cook, stirring constantly, for 2 minutes. Gradually stir in beef broth, stirring and cooking until thickened and smooth.
Heat remaining 1 tablespoon of butter and 1 tablespoon olive oil in a skillet or saute pan over medium heat; brown meat strips and onion on all sides.
Add meat and onions to the thickened beef sauce. Cover and cook on low for 10 minutes; stir in sour cream in heat through but do not boil.
Serve over noodles, pasta or rice