Add the rigatoni to salted boiling water, setting the timer to 2 minutes less than the packet's recommended cooking time.

Heat the olive oil in a pan over low/medium heat. Add the diced onion and gently fry for around 5 minutes until softened (not caramelised). Add the garlic and fry for an additional couple of minutes once the onions have softened.

Add the drained tuna, cream cheese, cheddar, and two ladles of pasta water to the pan. Stir until the cheese melts and a creamy sauce forms. Add extra pasta water as necessary to achieve the desired consistency.

Stir the lemon juice and dijon mustard into the sauce, then season with salt and lots of pepper.

Pour the rigatoni, sweetcorn and creamy tuna sauce into a baking dish (around 12 inch x 10 inch). Stir to incorporate everything and top with the remaining cheddar. Pop under the grill for 10 minutes, or until the cheese is golden brown and crispy.

Top with fresh parsley to serve.