Preheat the oven to 220°C, line a large baking tray with foil and spray with low-calorie cooking spray. Place the tomato halves on the baking tray in a single layer, cut side up. Spray with more low-calorie cooking spray and season with salt and black pepper. Roast in the oven for 20 minutes until they have wrinkled a little. Remove and set aside.
Meanwhile, cook the macaroni in a medium saucepan of boiling water for 8- 10 minutes, or according to the packet instructions, until al dente. Drain well and return to the saucepan, cover with a lid and set aside off the heat.
Spray a large, deep frying pan with low-calorie cooking spray and place over a medium heat. Add the onion and garlic and fry for 5 minutes until softened a little.
Add the stock cube to the water. Add the diced chicken, stock, basil and oregano to the pan and simmer, uncovered, over a medium heat for about 20 minutes, until the stock has reduced a little and the chicken is cooked right through. There should be no sign of pinkness and the juices should run clear.
Remove the pan from the heat and stir in the cream cheese until it has completely blended in. The sauce should be the consistency of single cream. If it is too thin, continue to simmer, uncovered, until it has reduced to the correct consistency. If it is too thick, stir in a little water.
Stir in 30g Parmesan cheese, the cooked macaroni and the spinach until just wilted. Add the roasted tomatoes and gently stir in. Season with salt and black pepper to taste.
Preheat the grill on the medium setting. Transfer the mixture to an 18 x 27cm ovenproof dish and spread out evenly. Sprinkle over the remaining Parmesan cheese and place under the grill for 5 minutes until the cheese is golden brown.
Serve with steamed green vegetables or other accompaniment of your choice.