MIX together the salt, sugar and lemon pepper; RUB on roast.
In a large covered pan (dutch oven), MELT the butter over medium heat; ADD coated roast and onion quarters; BROWN evenly.
ADD carrots, garlic salt, celery leaves and wine; COVER; BAKE at 325° F for 3 1/2 hours.
REMOVE beef from pan, RESERVING strained liquid; WRAP beef in aluminum foil; REFRIGERATE overnight.
ADD cornstarch to reserved liquid to thicken; STIR well.
In a medium skillet, MELT butter; ADD mushrooms and onion rings; SAUTE until softened, SEASONING to taste.
REFRIGERATE sauce separately from roast.
SLICE beef very thinly; ARRANGE in a casserole dish; POUR sauce over beef.
COVER; HEAT in oven at 350° F for 45 minutes.
Per Serving (excluding unknown items): 860 Calories; 51g Fat (59.7% calories from fat); 62g Protein; 16g Carbohydrate; 2g Dietary Fiber; 205mg Cholesterol; 873mg Sodium. Exchanges: 1/2 Grain(Starch); 8 Lean Meat; 2 Vegetable; 5 Fat; 0 Other Carbohydrates.