Gather and prep all ingredients and set the oven to 375°F.
Cook the lasagna noodles in salted water until just tender. Drain and lay flat on parchment paper.
In a large skillet, melt 1 Tbsp butter over medium heat. Sauté onion, celery, and garlic for 5-6 minutes.
Stir in shrimp, imitation crab, spinach, lemon juice, and Cajun seasoning. Cook until shrimp turn pink.
In a small bowl, stir together cottage cheese and parsley. Set aside.
In a medium saucepan, melt ¼ cup butter over medium heat. Whisk in flour and cook for 1 minute.
Gradually whisk in milk until smooth. Bring to a simmer and cook until thickened, about 5 minutes.
Spread a thin layer of the seafood sauce on the bottom of a baking dish.