Slice the onion thinly and cut the spinach into 4cm pieces after removing the roots.

Heat butter in a frying pan over medium heat, add onion and sauté until softened. Add canned tuna and spinach, then stir briefly.

Add flour and stir until no dry flour remains. Gradually add milk while stirring, cooking over medium heat until a light thick consistency forms. Add consomme, salt, and pepper, and mix well.

Boil water in a pot, add salt (not listed in ingredients) and cook spaghetti 1 minute less than package instructions. Drain well.