Flash Marinate the chicken with 4 dashes cajun seasoning, 2 dashes paprika and salt according to taste. Cajun seasoning already contains salt so you need to keep that in mind. This step is totally optional, however, flash marinating and than braising the chicken does build up excellent flavors. So, if you have a few extra mins on hand do this step.
Now, set the Instant Pot on SAUTE and set it on HIGH. Add oil. When the oil becomes moderately hot add the flash marinated chicken pieces and braise (fry them) them both sides until lightly golden or golden brown. Set them aside. You'll have some bits and crumbs sticking at the bottom of the pot while braising the meat, that's perfectly normal. Moreover. we'll be de-glazing the pot very well before pressure cooking.
Use the same oil, add more if needed. Keep the SAUTE settings to NORMAL. Add the chopped onions and saute until they begin to become translucent.
Now, add the colored bell peppers along with the celery and saute for 1-2 minutes.
Next, add the Cajun seasoning ( I mixed in the paprika too in the cajun seasoning just before adding). Mix everything well.
Add back the braised chicken chunks to the pot and give everything a very good mix.
In the meantime rinse the long grain white rice with enough water several times until you see clear water running through. This step is very important. It helps make the rice fluffy and prevents them from becoming messy, sticky and gooey. The surface starch of the rice is all drained out this way. Also, drain the rinsed rice very well. There should not be any excess water left.
Come back to the pot and add exactly 2 cups + additional 50 ml water and mix well. At this point de-glaze the pot really well with the help of a spatula. There should not be any bits and crumbs stuck at the bottom of the pot. De-glazing the pot well will prevent the BURN message.
Add the tomato paste and mix well again.
Next, add the rice and gently mix the grains in the water. Avoid over mixing, it will break the rice grains.
Check the seasoning and add salt if you need to.
Close the lid of the pot and seal the valve. Pressure Cook on HIGH for 5 minutes.
After 5 minutes when the Instant Pot begins to beep wait for 10 minutes natural pressure release. Than, release the rest of the pressure manually.
Open the lid carefully and fluff the Cajun rice gently with the help of a fork. For best result allow the Cajun Chicken and rice to rest for 10 mins before serving. This helps the rice become more fluffy. Enjoy!