Preheat oven to 350 degrees Fahrenheit.

In a small bowl or dish, combine the onion powder, garlic powder, paprika, 1 teaspoon of the salt, and pepper.

Next, in a bowl, add the cream cheese, parmesan cheese, and mozzarella cheese.  Stir in the mayo and artichoke hearts. 

Prep the spinach by cutting the stems off, washing it, drying it, and chopping it.  In a pan, heat a tablespoon of butter on low-medium heat.  Add the spinach to the pan.  Cook the spinach until it starts to wilt.  Add the spinach to the cheeses and stir until combined.  

Using a sharp knife or kitchen scissors, cut a pocket on the side of each chicken breast.  Make the pocket large enough to stuff a generous amount of the filling in the chicken.  Sprinkle a little bit of salt on the inside of the pocket.  

Rub the outside of the chicken with some oil, and then with the prepared spice run.

Stuff the inside of the chicken with your prepared filling.  Your stuffing should be facing up so that it doesn't spill out when cooking. 

Bake in the preheated oven for about 50 to 55 minutes, or until the chicken registers 165 degrees Fahrenheit internally.