Preheat your oven to 400°F.
Cut the end off a head of garlic to expose the cloves.
Coat it with olive oil, salt, and pepper, then wrap it in foil.
Roast for 40 minutes.
Dice the small onion and set it aside.
Bring a pot of salted water to a boil.
Blanch the spinach by submerging it until it wilts, then transfer it to ice water.
Prepare an oven-proof dish with non-stick spray.
Combine the cream cheese, sour cream, spinach, garlic, mozzarella, parmesan, gouda, cheddar, salt, and red pepper in a large bowl.
Mix well to combine all the ingredients thoroughly.
Spread the mixture evenly in the prepared baking dish.
Top with extra parmesan cheese.
Bake in the preheated oven for 10-12 minutes until golden and bubbling.
Let it cool for 5 minutes before serving.