Place the shrimp, cajun seasoning, and half of the oil in a mixing bowl and set it aside to allow the shrimp to marinate.
Dice up the onions and bell into thin strips.
Place the remaining oil into a skillet. Once the oil is hot, add the onions and peppers and cook on low heat.
Saute the vegetables until they begin to become soft and slightly charred on the edges. This should take about 10 minutes.
Move the cooked onions and peppers to one side of the pan and toss the marinated shrimp in. Allow them to cook completely. This should take between one and two minutes on each side.
Add a generous amount of shrimp and fajita vegetables to a tortilla shell. Garnish the Shrimp Fajitas to your liking and enjoy!