Wash and sort spinach. Collapse completely in boiling salted water and drain. Grate the parmesan. Peel garlic and press it through a garlic press. Wash lemon, grate peel and squeeze juice.
Roughly chop the spinach, capers, olives and anchovy fillet. Puree everything in a blender. Add olive oil bit by bit. Fold in parmesan, garlic and lemon peel. Season to taste with salt, pepper and 1-2 tablespoons of lemon juice.