Begin by slicing your fresh zucchini into even rounds, about 1/4 inch thick. Place the slices in a colander, sprinkling salt over them to draw out excess moisture. Allow the zucchini to rest for 15 minutes. Pat them dry with a paper towel.

In a medium bowl, whisk together the heavy cream, sour cream, Italian seasoning, onion powder, salt, and black pepper until combined. Melt butter in a skillet over medium heat and sauté freshly minced garlic until fragrant, about 1 minute. Add the cream mixture to the skillet, stirring continuously for 3-4 minutes until the sauce thickens slightly.

Once the sauce is warm, stir in the grated mozzarella cheese until it melts completely, creating a creamy, smooth texture. Keep stirring for another minute.

Take a buttered baking dish and layer the pat-dried zucchini slices evenly across the bottom. Pour the creamy sauce over the top, ensuring even coverage.

Sprinkle the remaining grated Parmesan and mozzarella cheese generously over the zucchini and sauce to form a golden-brown crust as it bakes.

Preheat your oven to 425°F (220°C) and bake for 18-22 minutes, or until the top is golden and bubbling.

Once baked, remove the dish from the oven and let it rest for 5 minutes before serving. Serve warm.