Pre-heat oven to 350°F and grease a 9-inch x 13-inch baking dish with butter.
In a large bowl, mix the cheddar and mozzarella; set aside.
In a small bowl, whisk the evaporated milk, egg, tomato paste, garlic and onion powders, mustard, thyme, Scotch bonnet pepper, 1 teaspoon salt and a generous pinch of black pepper until very well blended.
Cook macaroni in boiling salted water, according to the package directions for al dente; drain and return to the pot.
Stir in the tablespoon of butter until melted; add half the cheese and stir until it’s fully combined and starting to melt.
Stir in the milk mixture until the pasta is evenly coated.
Pour the pasta into the buttered dish; spread it evenly and sprinkle the rest of the cheese on top.
Place in pre-heated oven and bake until the top is bubbling and golden brown; 35 to 40 minutes.
Remove from the oven and let rest for at least 10 minutes to help firm up.