Cook potatoes and onions with 2 teaspoons salt in boiling water for 5 minutes. Drain. Slice franks; mix potatoes, onions, franks, flour, salt, butter, 1 can of the tomato sauce, cheese and parsley together. Spoon into 2-quart casserole. Pour remaining can of tomato sauce over. Bake for 35 minutes at 375 degrees F.