In a small saucepan, simmer all marinade ingredients for 10 minutes. If it reduces down too much, add more chicken stock. You should have at least 1 1/2 cups of marinade.
Rub the tenderloin with salt.
Put the salt rubbed pork and marinade in a zip lock for at least 1 hour and up to over night.
Put pork in a roasting pan fat side up. Top with thyme and rosemary sprigs.
Pour the marinade over pork tenderloin.
Roast the marinaded covered pork in the oven for 10 minutes at 475℉ uncovered.
Turn the temperature down to 350ºF and roast at the lower temperature for 20 minutes per pound. The internal temperature should reach 145ºF.
Remove from oven and tent with tin foil for 10 minutes.
Slice thinly and serve.