Preheat the oven to 350°F.
Bring a large pot of salted water to a boil, then add the macaroni and cook for about 8 minutes or until just al dente. Drain off the water and set it aside.
In a large bowl, mix together mayo, cheddar cheese, mozzarella cheese, sour cream, and a pinch of salt and pepper.
Add the cooked macaroni to the mixture and mix until everything is evenly combined.
Grease an 8×8 inch baking dish with cooking spray or butter.
Transfer the macaroni mixture to the baking dish and spread it out evenly.
Sprinkle the top with a bit of extra cheddar cheese and some cracked black pepper.
Bake in the preheated oven for 20-25 minutes or until golden brown on top.
Remove from the oven and let cool for 5 minutes before serving.