1. In a pot bring water to boil. Season with salt and add the pasta. Cook for around 9 minutes or till al dente. Drain in a colander and set aside.
2. In a pan heat oil on medium heat and add the red pepper and garlic. Saute for a few minutes or till garlic turns fragrant. Add the cooked pasta and mix well till combined.
3. Pour the cheese sauce and continue to stir and mix till all are well combined. Put in the pineapple pieces and again mix.
4. In a serving bowl, serve the Mac and cheese garnished with more pine apple pieces, red pepper, green onion, dry herbs and bread crumbs if desired or enjoy it as it is.