Preheat your oven to 400°F. Grease a 2-quart baking dish lightly with butter or non-stick spray.

In a medium saucepan over medium-high heat, melt the butter. Add minced garlic and chopped onion. Cook, stirring often, until the onion softens, about 5 minutes.

Stir in the cayenne pepper, onion powder, and heavy cream. Let the mixture simmer for about 5 minutes until it thickens slightly. Add the drained spinach, salt, pepper, 1/3 cup of the Parmesan cheese, sour cream, and the cream cheese. Mix until thoroughly combined.

Transfer the mixture into the prepared baking dish. Sprinkle breadcrumbs and the remaining Parmesan cheese evenly on top. Bake in the preheated oven for 15-18 minutes or until the top turns golden and the cheese bubbles.