Clean and wash the spinach. Steam covered in little boiling salted water for about 2 minutes. Drain well. Grate parmesan. Peel and chop the garlic. Wash and dry lemon. Grate the peel, squeeze the juice
Roughly chop the spinach, capers and olives. Puree with parmesan and garlic in a blender, adding oil little by little. Add lemon zest. Season pesto with salt, pepper, lemon juice and sugar