In a saucepan, sauté the chopped onion, bell pepper, butter, and garlic.
Add the crawfish tails and Cajun Boy seasoning. Make sure to add water to the bag of crawfish tails to get all the buttery fat into the pot.
Once the mixture comes to a boil, simmer for 10 to 15 minutes, making sure to add plenty of Cajun Boy Creole seasoning to the mix.
Add 3/4 of the block of Pepper Jack cheese, stirring until all the cheese is melted evenly, for approximately 5 minutes.
Lightly grease a small Pyrex deep dish baking pan.
Fill 6 flour tortillas with the crawfish mixture and roll into the baking dish.
Use the remaining crawfish to cover all 6 tortillas, then top with shredded Monterey cheese and bake at 350°F for 25 minutes, covered.
Remove from oven and let sit for 5 to 10 minutes. Serve with chopped onion tops garnish and sour cream if preferred.