Steps
1. Preheat your oven to 375°F (190°C).
2. In a skillet, heat olive oil over medium heat and sauté garlic until fragrant.
3. Add the chopped spinach and bell peppers, cooking until soft (about 3-4 minutes).
4. Season with salt, pepper, and Italian seasoning, then remove from heat.
5. Slice the pork tenderloin lengthwise, creating a pocket, and season the outside with salt and pepper.
6. Stuff the pork with the spinach and pepper mixture, pressing it in well.
7. Place the stuffed tenderloin on a baking sheet and sprinkle with Parmesan cheese if using.
8. Bake for 25-30 minutes or until the pork reaches an internal temperature of 145°F (63°C).
9. Let rest for 5 minutes before slicing and serving.