Combine rice, water, taco seasoning, and tomato powder in a 7x3-inch cake pan or oven-safe bowl. Stir to ensure rice is covered.
Toss chicken breast pieces with garlic salt and black pepper in a bowl.
Turn on a multi-functional pressure cooker (such as Instant Pot) and select Saute function. Melt butter. Add salsa and chicken; stir to combine. Pour black beans and corn into separate small silicone bowls. Place bowls on opposite sides of the Instant Pot, nestling the chicken between them. Place elevated trivet into the Instant Pot. Set the container of rice on top of the trivet. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 4 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure using the natural-release method according to manufacturer's instructions, about 11 minutes. Unlock and remove the lid. Remove rice from trivet. Remove trivet. Blend corn and black beans with the chicken.
Add equal amounts of rice to 4 serving bowls. Top with chicken mixture.