Preheat the oven to 325 degrees F (165 degrees C).

Place onion, celery, and carrot in a large, shallow roasting pan.

Place turkey, breast-side up, on top of vegetables in the roasting pan. Pat outside and inside of turkey dry with paper towels.

Combine salt, black pepper, and cayenne pepper in a small bowl. Season inside of turkey with about 1/3 of the salt mixture. Fold wing tips under bird.

Melt butter in a small saucepan over medium heat until edges turn golden, about 2 minutes. Add rosemary and sage; cook and stir until fragrant, about 1 minute.

Place rosemary and sage inside cavity of turkey; reserve melted butter. Tie turkey legs together with twine.

Brush melted butter over turkey. Season with the remaining salt mixture.

Bake turkey, uncovered, in the preheated oven until no longer pink at the bone and juices run clear, about 3 hours. An instant-read thermometer inserted into the thickest part of the thigh, near the bone should read 180 degrees F (82 degrees C).

Remove turkey from the oven and allow to rest in a warm area for 10 to 15 minutes before slicing.