First, peel and finely chop the onions, parsley also finely chop. Cut the tomatoes into small pieces, strain the tuna.
Mix the fish well in a bowl with the chopped onions, parsley, tomatoes, grated mozzarella and cream cheese, season with salt and pepper.
Cut the baguette lengthwise. Spread the tuna mixture on both halves of the baguette and sprinkle with the shaved parmeasan.
Bake in a preheated oven at 180 to 200 °C (convection oven) for about 15 minutes.
Serve the baguette while still warm.