I've experimented with salad dressings quite a bit over the years. My current favourite starts with three big table spoons full of plain soya yogurt, a teaspoonful of marmite or propriety yeast extract well mixed in and finely chopped garlic and chili. After that I just chop up whatever salad stuff I have until the bowl is full. I usually include a tomato for sweetness and part of a red or yellow capsicum for colour.