Start with preheating the oven at 375°F (190° C). Then grease it with a baking brush.
Meanwhile, sauté the onion and garlic in oil until they release fragrance.
Then mix cream cheese, sour cream, mayonnaise, and cheeses in a bowl.
Now, fold in the spinach mixture and season it with spices. Then stir them well.
Let the dip bake for 20 to 25 minutes or until it becomes golden and bubbly. That's it. Serve it hot.