Prepare the cuttlefish, removing the hard parts and the ink. Wash them and leave to drain. Prepare, wash and chop the spinach into large pieces. Sauté for 5 minutes in half of the oil with 1 finely chopped onion. Now stuff the cuttlefish with the spinach. Close them carefully and place them in a pan with the remaining oil and chopped onions. Sauté for a few minutes and then ‘quench’ with the wine. A few minutes later, add the chopped tomatoes, finely chopped fennel, seasonings and a little water. Leave to cook over a low heat until the cuttlefish are tender.