Grease a 9-inch cast iron skillet with 1 tablespoon of oil or butter. Set aside. (Use more butter or oil if you need it.)
Season the broccoli florets with the salt, pepper, cayenne pepper, paprika, parsley flakes and onion powder.
Arrange in a single layer in the cast iron skillet.
Bake for 15 to 20 minutes, or until roasted through and beginning to brown.
While the broccoli florets are baking, brown the Cajun trinity of onion, bell pepper and celery in a saucepan.
When the trinity is browned, add the garlic and cook for 1 additional minute, or until fragrant.
Stir in the tapioca starch, and cook for 1 additional minute, or until the starch browns slightly.
Stir in the milk and cheeses.
Remove the cooked broccoli from the oven, and let cool slightly.
Rough-chop half of the broccoli into larger pieces, then place the other half of the broccoli in a food processor or blender. Pulse for about 30 seconds, or until the broccoli florets crumble.
Stir the broccoli to the cheesy dip mixture.
Pour into a small, greased casserole dish.
Bake for 10 to 15 minutes, or until bubbly and browned slightly.