In a 2 1/2 quart microwavable casserole, stir polenta, salt and cold water together. Microwave on high, uncovered, for 7 minutes. Stir well, cover with waxed paper and cook an additional 7 minutes on high. Stir well and cook another 3 minutes. Stir in butter and pepper. Let stand 5 minutes before serving.
Note: This is a great way to make polenta without standing and stirring. Good plain or top with your favorite sauce or grated cheese.