If serving the gnudi with the tomato sauce, start with that. Heat up olive oil in a pot, add diced onion, carrot and celery and let them cook for 5-8 minutes. Add tomato passata and some water (half the bottle) let it cook on low heat for at least 30 minutes.
Cook the frozen spinach in boiling water, then drain it as much as possible to remove excess water. Cut it finely.
To make the tofu ricotta, in a blender add tofu, miso paste, lemon juice, olive oil, salt pepper and nutmeg and some water to help blend, blend until smooth.
In a bowl add the spinach, the tofu mixture, salt, pepper, nutmeg, cornstarch, nutritional yeast and mix to combine. Form little balls with your hands and coat them in flour.
Cook them in boiling water until they rise, a few minutes only. Serve them with the tomato sauce.