Preheat the Oven: Preheat your oven to 400°F (200°C).

Prepare the Pork: Pat the pork tenderloin dry with a paper towel. Rub 1 tbsp of olive oil over the tenderloin, then season with salt, pepper, and thyme or rosemary if desired.

Roast the Pork: Place the tenderloin on a baking sheet or roasting pan. Roast for 20-25 minutes, or until the internal temperature reaches 145°F (63°C). Remove and let it rest for 5-10 minutes before slicing.

Cook the Lentils: While the pork is roasting, rinse the lentils under cold water. Add them to a pot with 2 cups of water and a pinch of salt. Bring to a boil, then reduce to a simmer and cook for 15-20 minutes, or until tender. Drain any excess water.

Sauté Spinach and Garlic: In a large skillet, heat 1 tbsp of olive oil over medium heat. Add minced garlic and cook for 1 minute until fragrant. Add the spinach, stirring until wilted (about 2-3 minutes). Combine the spinach with the cooked lentils and season with salt and pepper.

Serve: Slice the pork tenderloin into medallions and serve with the garlic lentil and spinach mixture.