Add the butter to the bowl of the instant pot, and press the saute button. When the butter is melted, add in the ground beef.
Cook the beef, breaking up as it cooks, until cooked through with no visible pink remaining.
Add the broth, milk, onion powder, and garlic powder to the pot. Whisk together until smooth & evenly combined.
Pour the rice into the pot, and using the back of a spoon gently push it so that it's all just below the liquid.
Without stirring, gently add the tomatoes & corn.
Close the Instant pot, turning the lid to secure and make sure the vent's set to the sealed position. Press the pressure cook button, and set the pot to cook on high pressure for 7 minutes.
As soon as the seven minutes are up, turn the vent to do a quick pressure release. Make sure to do it so the rapidly escaping steam doesn't hit your hand or arm.
Remove the lid from the instant pot, set aside. Using a sturdy spoon, give the beef & rice a hearty stir- fluffing the rice as you do.
Stir in the cheeses until completely melted & evenly combined.
Salt & pepper the mixture, to taste. Ladle it into bowls, and serve immediately.