Pull spinach leaves from stems and soak in several changes of cold water until free of soil.
Cook spinach covered with just the moisture clinging to the leaves and 2 tsp salt until very tender (10 minutes or more). Drain and cool.
Squeeze spinach very dry by handfuls, chop very fine, and put in a bowl.
Chop tuna and add to the bowl with the chopped anchovy.
Soak bread in milk.
Add eggs to the bowl, then add Parmesan, bread crumbs, salt, and generous grindings of pepper.
Squeeze soaked bread so the milk runs back into the dish, then add the bread to the bowl and mix into a homogeneous mixture.
Shape into a roll and wrap in cheesecloth as directed for the preceding roll recipe.
Put the roll in an oval pot or fish poacher, cover with water, cover the pot, and bring to a boil over medium. Reduce to a steady gentle simmer and cook 35 minutes.
Lift out carefully, remove cheesecloth, and let cool completely to room temperature. Do not refrigerate.
Slice under 1/2 inch thick and arrange overlapping on a platter. Drizzle with olive oil and lemon juice. Top each slice with a thin lemon slice and a tiny carrot disk.