Adjust racks to middle and top positions and preheat oven to 400 degrees. Line a baking sheet with foil. Wash and dry produce.
Remove ribs* from package and place on prepared sheet. Top ribs with any remaining sauce from package, then sprinkle with half the chili powder (you’ll use the rest later). Top ribs with a second sheet of foil; crimp edges of foil to create a packet.
Mince jalapeño, removing ribs and seeds for less heat.
Place 3 TBSP butter (6 TBSP for 4 servings) in a small microwave-safe bowl. Microwave until melted, 30 seconds.
In a separate small bowl, combine half the melted butter with cream cheese, half the cheddar (you’ll use the rest later), and up to half the jalapeño to taste.