Preheat oven to 400ºF. Combine salt, Italian seasoning and black pepper. Rub all over tenderloin and let sit for a few minutes.
Heat an oven-proof skillet over medium-high heat. Add tenderloin and cook, turning occasionally, until golden brown all over, about 6-8 minutes total. Transfer pan to the oven and top with rosemary if desired.
Bake uncovered for 13-15 minutes, or until the internal temperature of the pork is 145ºF. Remove from oven, being careful of the hot pan handle. Transfer tenderloin to a cutting board and tent with foil. Allow to rest 5-10 minutes.
Slice tenderloin and serve with sauce if desired.
This dish has great flavor on it own. We also love to serve it with A-1 sauce or this apricot sauce below. Apricot sauce (optional):
1/2 cup chicken broth
1/2 cup apricot jam
Heat the chicken broth, apricot jam and rosemary over medium heat in a pan. Simmer about 4 to 6 minutes. Slice tenderloin and serve with sauce. Garnish with rosemary if desired.