In a bowl add the remaining olive oil, the lemon zest, garlic and rosemary. Salt and pepper the mix and add the pork tenderloin. Turn the pork tenderloin to make sure all sides are covered with the mixture.
Fill a large pot of water and add the lentils and bring to a boil. Lower the heat to a slow simmer and cook for another 20 minutes, or until the lentils are tender and cooked. Rinse and set aside.
Meanwhile in a large salad bowl, mix the Dijon mustard and the balsamic vinegar. Add the salt and pepper and 4 tablespoons of the olive oil. Whisk the sauce together until smooth. Add the mushroom and the lentils. Mix well and let it rest.
In a skillet over medium heat sear the pork tenderloin until all sides are golden, around 15 minutes. Insert a knife into tenderloin to insure the meat is cooked and no juices are running out. Take it off the heat and place in a cutting board, cover with aluminum foil and let it rest for 5 minutes.
Return the skillet to medium heat, add the red wine and deglaze the skillet. Pour the mixture over the mushroom and the lentils. Mix well. Add the spinach and cherry tomatoes and stir well.
Cut the meat in small rounds and add to the spinach lentil salad bowl.
Sprinkle the ½ lemon juice over the whole dish and serve.