Finely chop the onions and sauté in a little oil. Add thawed spinach leaves and sauté briefly. Let cool and stir in yogurt. Season with salt and pepper, done!
I copied this recipe from my Persian father-in-law. It`s simply delicious, goes super fast and is eaten cold, e.g. as a starter with warm flatbread. In Persia everything is usually served together, so it can also be enjoyed as a side dish, e.g. to a rice dish.
In the original it is definitely prepared with fresh spinach and possibly other spices, but it also tastes really delicious!