Preheat oven to 350°
Thaw and drain the frozen spinach. Be sure to squeeze ALL of the liquid out of the thawed spinach. Set it aside until it's time to assemble the dip.
Cut the artichoke hearts into bite-sized pieces. Set aside until it's time to assemble the dip.
Chop the pistachios into small pieces. Set aside until it's time to assemble the dip.
Mix the cream cheese with a mixer or by hand until creamy.
Add the garlic powder, onion powder, seasoning salt, and black pepper.
Stir in the parmesan cheese, mayonnaise, and 1/4 cup of mozzarella cheese.
Mix in the spinach and artichoke hearts.
Spray a shallow baking dish with non-stick cooking spray.
Spoon the spinach artichoke mixture into the baking dish and press down lightly with your hands.
Top with the remaining mozzarella cheese and sprinkle the pistachios over the top.
Bake uncovered for 15-20 minutes.
Serve hot with toasted baguette slices and crackers.