Preheat the oven to 350 F. In a medium-sized bowl, combine the cream cheese, cheddar cheese, mayo, chopped onion, chopped jalapenos, mustard powder, paprika, salt, and pepper. Mix until well combined.

Microwave mixture for a minute at a time until melted and pour into a baking dish. Bake for 20-25 mins or until bubbly and slightly brown on top.