1/2 onion, chopped
3 to 6 tbsp. mayonnaise
1/2 cucumber, skin on, thinly sliced and quartered
1/2 apple, chopped, peeled or not
1 tbsp. lemon juice
1 or 2 carrots, slightly cooked, still crunchy, thinly sliced

Mix everything and refrigerate for a few hours or overnight.