Cook the pasta until it is slightly underdone. This will ensure that it doesn't become too soft in the oven.

In a frying pan, sauté the onions, mushrooms, red peppers, and red chillies until they become tender and golden.

Add the capers, dried oregano, celery salt, and pepper to the pan, and continue to cook for a few more minutes.

Next, incorporate the tinned tomatoes and passata into the pan, allowing the flavors to meld together. Simmer the mixture for a few minutes until it thickens slightly.

Drain the canned tuna and add it to the sauce. Gently stir to combine all the ingredients.

Now, it's time to assemble the bake. Stir in the cooked pasta, ensuring that it is well-coated with the sauce.

Transfer the pasta and sauce mixture into an ovenproof dish.

Sprinkle the grated cheddar cheese evenly over the top of the pasta.

Bake the dish in a preheated oven until the cheese turns golden and bubbly.

Remove from the oven and let it cool for a few minutes before serving.