Heat the extra virgin olive oil in a large stock pot over a medium flame. Add the chopped onion, shallot and garlic, lower the heat and sauté slowly for 4 to 5 minutes to soften the onions but not brown.
Add the potato, season with salt and sauté for an additional 4 to 5 minutes.
Add the zucchini and continue to cook for another 4 to 5 minutes, stirring occasionally. Add the lemon juice a little at a time and taste as you go. Stop when you think it's lemony enough!
Add the water, increase the heat and bring the soup to the boil.
Reduce the heat, partially cover the pot and simmer for 20 to 30 minutes until the vegetables are soft.
Allow the soup to cool slightly transfer to a blender and blend until completely smooth.
Season with cracked pepper and serve warm in glasses with a layer of olive oil over the top.