Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish. Channel your inner Cajun as you do so, just for fun.
Heat a large skillet over medium heat, and melt the butter. Add the onions, bell peppers, and garlic. Sauté until tender, about 5 minutes, or until your kitchen smells like heaven.
Stir in the flour until it looks like a delicious roux-y mess. Gradually add half-and-half and chicken broth, whisking continuously to avoid lumps.
Add tomatoes, Cajun seasoning, thyme, and basil. Allow the mixture to thicken and bubble gently for 5 minutes. Taste and add salt and pepper as needed.
In a separate bowl, combine shrimp, crabmeat, and scallops. Add half of the sauce to the seafood mixture, reserving the other half.
Spread a thin layer of the reserved sauce in the prepared baking dish. Place a layer of lasagna noodles, followed by a layer of the seafood mixture, and sprinkle with mozzarella and pepper jack cheese. Repeat until you've used all the ingredients, ending with a layer of noodles.
Top the lasagna with the remaining sauce, and generously sprinkle with Parmesan cheese. Cover with aluminum foil, making sure the foil doesn't touch the cheese (we wouldn't want any cheese-napping, now would we?).
Bake for 45 minutes, or until bubbly and golden. Let it rest for 15 minutes to avoid a molten cheese disaster. Sprinkle with chopped parsley and serve.