Grate cheese and mix evenly. Boil macaroni in the water to desired tenderness. Drain and immediately add margarine, 3/4 of the cheese and sour cream. Stir, letting the heat from the macaroni melt the margarine, cheese and sour cream. Add nutritional yeast flakes, lemon juice, salt, and milk. Add additional seasonings to taste. Place in a casserole dish and add remaining grated cheese to the top. Cover and bake at 350o about 30 minutes (cheese on top should be melted). Uncover and turn the oven to broil. Broil macaroni to desired brownness. Remove from oven and serve.