Zest the lemon first and set the zest aside. Squeeze the lemon and measure 1 1/2 tablespoons of juice for the dressing.
In a tall mixing cup or the bowl of a blender, combine the cottage cheese, lemon juice, Dijon, mayonnaise, lemon zest and garlic powder. Blend or use an immersion blender until the mixture is completely smooth and slightly fluffy — this creates a silky, mayo-tuned dressing while keeping the cottage cheese base.
Taste the dressing and season with half the salt and pepper. Remember you can always add more after mixing with the chicken.
Place the shredded chicken in a large bowl. Add the diced red onion, chopped celery, and chopped fresh dill, reserving a tablespoon of celery and dill for garnish if you like a bit of crunch on top.
Pour the blended cottage cheese dressing over the chicken and vegetables. Gently fold with a spatula until everything is evenly coated. Avoid overmixing so the chicken keeps some texture.
Cover and refrigerate the salad for at least 20–30 minutes to let flavors meld and the dressing firm slightly; this improves the texture and flavor balance.
Before serving, give the salad a quick stir, then taste and adjust salt and pepper as needed. Garnish with the reserved celery and dill. Serve chilled on bread, in a wrap, with crackers, or atop mixed greens.