Preheat the Oven: Preheat your oven to 375°F (190°C). Grease or lightly butter a 9x9-inch baking dish.
Sauté the Spinach: In a medium-sized skillet, melt butter over medium heat. Add the chopped spinach and sauté until wilted and tender, about 2-3 minutes. Drain excess moisture from the spinach and set it aside.
Prepare the Creamy Base: In a large mixing bowl, combine the softened cream cheese, sour cream, mayonnaise (if using), and Parmesan cheese. Mix until smooth and creamy. Stir in the minced garlic, onion powder, salt, and pepper to taste.
Add Crab Meat and Spinach: Gently fold in the crab meat and sautéed spinach into the creamy base, making sure everything is well combined.
Top and Bake: Transfer the mixture to the prepared baking dish. If desired, sprinkle shredded mozzarella cheese on top for extra cheesiness, or top with breadcrumbs for a crispy crust. Bake in the preheated oven for 20-25 minutes, or until the dip is bubbling and golden on top.
Serve and Enjoy: Remove the dip from the oven and let it cool for a few minutes before serving. Serve with your choice of crackers, bread, or fresh-cut vegetables. Enjoy the creamy, savory goodness of your homemade spinach dip with crab meat!