In a food processor, add cottage cheese, sugar, milk, yogurt, vinegar, lemon pepper, minced onion, and salt if using. Blend together until smooth.
Add slaw into a glass or plastic bowl and pour cottage cheese mixture over slaw. Stir together to completely coat the slaw. {You might not need to add all of it because the slaw with release some water while it sits, so don't use too much sauce or you'll have soupy slaw}.