Preheat the oven to 375° F. Butter a 9x13-inch baking dish.To the baking dish, add the dry pasta, half of each shredded cheese, the milk, sour cream, ground mustard, cayenne, and 1/3 cup water. Season with salt and pepper. Stir to combine. Push the cubes of brie into the pasta. Tightly cover the baking dish with the foil. Bake for 25 minutes. Meanwhile, in a bowl, mix the Ritz with the butter, onion powder, garlic powder, and paprika. Uncover the pasta and sprinkle over the remaining shredded cheese. Top evenly with the Ritz. Bake another 15-20 minutes, or until the cheese is melted and bubbly. Remove from the oven. Dig in and enjoy!