Preheat oven to 200°C. Over a medium heat, melt the butter in a pan. Add the garlic, and cook for 1-2 minutes. Add the spinach, and cook for a further minute or until wilted. Squeeze over the lemon juice and set aside.
In a bowl, mix together the onion powder, cream cheese, Sour Cream, and grated cheeses. Add the spinach mixture, mix well to combine. Season to taste.
Cut a small layer off the top of the bread loaf. Hollow out the loaf, keeping the bread to the side. Transfer the dip to the crust, and place on a baking tray. Spread the bread chunks around the loaf, drizzle with oil, and place into the oven. Cook for 10-15 minutes, or until bread is golden.
Serve the dip with the bread pieces and crudite vegetables.