First, combine homemade the spices for the homemade cajun seasoning in a small bowl. Mix and set aside.
Then, add shrimp and andouille sausage to a large bowl and sprinkle on 1 tablespoon of cajun seasoning. Toss everything together and set it aside.
Turn on the Instant Pot's saute feature. Then add olive oil. When olive oil is fragrant, add onion and garlic and saute for 3-5 minutes or until onions are translucent.
Turn off the saute feature and then add in white rice and mix. Add in peppers, 2 tablespoons of cajun seasoning, diced tomatoes, and chicken broth, and stir to combine.
Close the lid and cook on high pressure >> for 8 minutes.
Quick-release pressure from the Instant Pot and immediately uncover. Add shrimp and andouille sausage to the pot, mix to combine. Place the cover back on and let steam for 10 minutes.
Uncover the Instant Pot and mix and give it a taste. Adjust the salt as needed. Serve and enjoy.