Preheat the oven to 400F
Pan-sear the tenderloin. Add the olive oil to a large deep skillet and heat over medium-high. Once the oil begins to shimmer, place the tenderloin in the pan. Pan sear until golden on each side, about 4 minutes on each side. Remove the pork loin from the pan and set aside.
Cook the string beans. Lower the heat to medium-low and add the butter. Once the butter has melted, add the garlic and cook until golden brown.
Add the string beans and ¼ cup chicken broth, then raise the temperature to medium-high and cook for 8 minutes more.
Make room in the center of the pan by pushing the string beans to the side. Place the oranges in the center of the pan and lay the pork over the oranges.
Place the pan in the oven and roast until the pork has an internal temperature of 140F, then remove JUST the pork and let it rest. The pork will continue to cook and should reach 145F before eating.
Return the string beans and the orange slices to the oven and raise the temperature of the oven to broil. Broil for 3-5 minutes more.
While the pork cooks, make the sauce. Sir the cornstarch into the chicken broth to make a cornstarch slurry, then set aside.
To a saucepan, add the orange juice, brown sugar, vinegar, butter and thyme. Mix well and bring to a simmer. Stir in the cornstarch slurry and continue to cook until the sauce has thickened. Remove from the heat, remove the thyme sprig, and mix in the orange zest.
Once the pork has rested for at least 8 minutes, slice, place on top of the string beans, pour the orange sauce over the pork, and serve immediately.