- Set a rack inside a large heavy roasting pan.
- Season turkey lightly inside and out with salt and pepper, then with spice mix, massage it into skin.
- Transfer turkey, breast side down, to prepared pan and refrigerate, uncovered, overnight.
- Remove turkey from refrigerator; let stand at room temperature for 1 hour.
- Heat oven to 375°F.
- In a medium bowl, mix celery, pepper, and onion.
- Fill turkey cavities with vegetable mixture, scattering any remaining vegetables over bottom of roasting pan.
- Brush turkey with oil.
- Roast turkey, basting occasionally, for 1 hour.
- Using paper towels, flip turkey.
- Roast, basting occasionally, about 1 to 1 1/2 hours longer, until an instant-read thermometer inserted into thickest part of thigh registers 165°F.
- Transfer to a platter.
- Let rest for at least 20 minutes before carving.
Serves 10.
Approximate Nutrient Analysis per serving (based on 12 pound turkey and no additional salt besides Cajun-Creole seasoning blend):
550 calories, 24 g fat, 5 g saturated fat, 260 mg cholesterol, greater than 2300 mg sodium, 9 g carbohydrate, 3 g fiber, 2 g sugar, 72 g protein