Preheat the oven to 325°F (165°C).

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

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

Combine the salt, black pepper, and cayenne pepper in a small bowl. Use about 1/3 of the mixture to season the inside of the turkey. Tuck the wing tips under the bird.

Melt butter in a small saucepan over medium heat until golden at the edges (about 2 minutes). Add rosemary and sage; stir until fragrant (about 1 minute).

Place rosemary and sage inside the turkey cavity. Reserve the melted butter. Tie the turkey legs together with kitchen twine.

Brush the melted butter over the turkey and season with the remaining salt mixture.

Bake the turkey, uncovered, in the preheated oven for about 3 hours. Use a meat thermometer to check that the thickest part of the thigh reaches 180°F (82°C).

Remove the turkey from the oven and let it rest in a warm place for 10-15 minutes before slicing.