1.Bring a large pot of lightly salted water to a boil
2.In a pan with olive oil fry minced garlic cloves for 1-2 minutes
3.Add fresh spinach, cook 4-5 minutes. Remove from heat and let cool. When cooled chop the spinach.
4.In a large bowl mix together ricotta, chopped spinach, parmesan cheese, lemon zest, salt, pepper and nutmeg.
5.When the water in the pot is boiling add the cannelloni. Cook for 6-7 minutes and transfer to cold water.
6.Heat oven to 180C/360f
7.Transfer the filling into piping bag and fill all cannelloni tubes.
8.Pour 4-6 tbsp of tomato sauce into the base of large baking dish (~20*30cm/8*12in). Lay the tubes, side by side. On top pour the reminding tomato sauce. And cover all with grated mozzarella cheese.
9.Cover baking dish with foil and bake for 15 min, after 15 minutes remove the foil and bake 15 minutes more.