Prepare the pork: Pat the pork tenderloin dry with paper towel. Season generously with salt, black pepper, garlic powder, and dried thyme, rubbing the spices into the meat.
Cook the pork: Heat 2 tablespoons olive oil in a large pan over medium-high heat. Add the pork tenderloin and sear on all sides until golden brown, about 2-3 minutes per side. Reduce heat to medium and continue cooking for 8-10 minutes, turning occasionally, until the internal temperature reaches 63°C. Remove from heat and let rest for 5-10 minutes before slicing into medallions about 1 cm thick.
Make the dressing: While the pork is resting, whisk together the olive oil, apple cider vinegar or lemon juice, Dijon mustard, honey, wholegrain mustard, salt and black pepper in a small bowl until well combined and emulsified.
Assemble the salad: In a large serving bowl or platter, arrange the mixed salad greens as a base. Top with sliced pears, radishes, and beetroot wedges. Add the sliced pork tenderloin, then scatter the feta cheese cubes and dried cranberries over the top. Sprinkle with toasted walnuts or pecans if using.
Dress and serve: Drizzle the honey mustard dressing over the salad just before serving, or serve the dressing on the side. Toss gently if desired, or serve as a composed salad.