1. Clean and devein the shrimps, chop finely, keep it aside.
2. Finely chop the onion and sauté it in a pan with the melted butter.
3. Sauté until the onions is translucent or for 5 minutes.
4. Add the shrimps and cook them along with the onions for 10 minutes
5. Generously season the shrimps with the mexi-cajun seasoning and cook the shrimps further for 10 minutes or until the shrimps turns pink.
6. In the meantime make the sauce by combining in a bowl, sour cream, light mayonnaise and mexi-cajun seasoning.
7. Warm the tortillas, and fill it with the shrimps and top it with the creamy salsa.
8. Serve the shrimps fajita tacos along with a glass of coke.