Trim fat from steak. Cut into 1 inch pieces. Spray a pan, heat over medium heat and cook the steak, half at a time, until brown. Place meat in a 3 1/2 or 4 quart crockpot. Combine soup, onion, tomato paste and lemon pepper in a medium bowl. Pour mixture over meat.

Add mushrooms. Cook on low setting for 8 to 10 hours (or high for 4 to 5 hours). Turn heat to high. Add frozen green beans and buttermilk. Stir, cover and cook for 30 minutes more. Meanwhile, cook fettuccine. Serve meat over fettuccine.