Preheat oven to 400 degrees. Grease a large cast-iron skillet with non-stick cooking spray. You can also use a 9x9 baking dish.
Bring a large pot of water to a rolling boil. Season with salt, it should taste as salty as the sea. Add the pasta and cook for 6 minutes. Drain the pasta in a colendar.
Add the cream, dijon, and salt to the pot you cooked the pasta in. Whisk until combined. Add the pasta to the cream mixture. Stir to combine.
Spoon half of the pasta into the prepared dish. Sprinkle with all of the cheddar cheese and half of the parmesan. Season with a little bit of salt and pepper. Spoon the remaining pasta on top and pour any remaining cream evenly over the top. Cover with remaining parmesan cheese. Season with a little bit of salt and pepper. Place in the oven and bake, uncovered for about 15 minutes until the pasta is aldente, the cream is bubbling, and the top is crispy and brown in places. Serve immediately.