Juice two of the oranges and all of the limes into a bowl. Whisk in ½ cup of olive oil, cumin, salt, and pepper. Add the garlic and cilantro.
8 limes, 2 oranges, 1 bulb garlic, 1 tablespoons ground cumin, ½ tablespoon kosher salt, ½ teaspoon ground black pepper, ¾ cup olive oil, ¼ cup cilantro1
Pour the marinade into a plastic bag and add the sliced oranges and tenderloin. Set aside in the fridge for six hours, (overnight if you can, but 6 hours will get you 90% of the way there).
1 orange, 1½ lbs pork tenderloin
Once the meat is done marinating, preheat your oven to 350°F, add the remaining ¼ cup of olive oil to a cast-iron pan, and heat over medium-high heat on the stovetop.
¾ cup olive oil
Take your tenderloin and place it in your hot pan allowing it 60 seconds or so on a side before giving it a quarter turn. After the third turn remove from heat and slide in your probe thermometer2.
Set the thermometer to 145°F and move the whole pan to the oven. It should take about an hour to reach the desired temp. Once done remove from the pan and allow to rest 15 minutes before cutting.