First combine the Greek yogurt, olive oil, lemon juice, minced garlic, herbes de Provence, garlic powder, salt, and pepper in a large bowl and stir well.
To marinate the pork tenderloin, place it in the bowl and coat it well with the marinade. Then, put in on a clean plate and cover tightly with plastic wrap and let it chill in the refrigerator for a minimum of 2 hours, or preferably overnight.
When ready to cook preheat the oven to 400℉ 205℃, and take the tenderloin out of the fridge and set it on the counter to warm up a little.
To cook the tenderloin, first preheat an oven-safe pan over medium-high heat on the stove. When the pan is hot, drizzle some oil on it and place the tenderloin in the pan. Sear the tenderloin for about 5-6 minutes, turning it occasionally to brown all sides evenly.
Transfer the skillet to the oven and bake for another 10-15 minutes, or until the meat reaches an internal temperature of 135 F for medium-rare or 145 F for medium. The baking time varies depending on how thick the meat is, so check it sooner if you have a thinner cut.
Remove from the oven and let the tenderloin rest for at least 5 minutes before carving.
Lastly, cut the pork into round medallions after letting it rest and enjoy right away. You can add some fresh herbs on top or have it with any sides you like, mashed potatoes and gravy, roasted vegetables, and a green salad.