Press Saute on a 6-quart Instant Pot. When the display reads “hot”, add the butter and allow it to melt.
Add the onions and jalapeno and saute 3-4 minutes, or until softened. Season with garlic powder, cumin, paprika, salt, and cayenne (if using).
Press Cancel, then add the tomatoes and broth, stirring well. Add the cream cheese cubes on top of the mixture; do not stir.
Secure the lid and pressure valve, and cook on Manual High Pressure for 1 minute. Perform a quick release, then carefully remove the lid.
Add the heavy cream and stir, then gradually add the shredded cheeses, 1 cup at a time, stirring well until it’s completely melted.
Allow the queso to thicken for a few minutes, then transfer it to a serving bowl. Garnish with jalapeno slices and diced tomatoes (if desired), and enjoy with a big bowl of tortilla chips.