Peel the onions, cut them into strips and fry them in a frying pan.
Drain and add the corn kernels and capers. Wash the tuna (only if it was pickled in oil) and chop it. Now add the tuna and fry it briefly.
Then deglaze everything with the white wine. Season with salt and pepper and add the herbs.
In the meantime, preheat the oven to 180°C. Add the cream to the tuna and stir well. Bring to a gentle simmer.
Add the garlic to the tuna at the very end. Now put the pasta uncooked in a gratin dish. Cut some of the mozzarella into cubes and place on top of the pasta. Stir the tuna mixture into the pasta and spread the rest of the mozzarella on top. Place the casserole in a hot oven and cook on low for about 20-25 minutes. Serve hot.