Sauté spinach with butter in a medium skillet over medium-low heat.
Remove and dry spinach with a paper towel.
Preheat oven to 375°F.
Chop dry spinach and sun dried tomatoes into course pieces.
In a large bowl, combine sour cream, cream cheese, garlic, salt, pepper, onion powder, Parmesan, tomatoes, spinach, and ½ of Mozzarella and Monterey Jack cheeses. Mix until well combined.
Grease an 8x8 baking dish and evenly spread dip into it. Cover top with remaining cheeses and and bake for 15-20 minutes until bubbling.
Change oven to broil and cook until cheese begins to brown to desire.