Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
- Toss the cubed sweet potatoes with 1 tablespoon of olive oil, salt, and pepper. Spread them evenly on the prepared baking sheet.
- Roast for 25-30 minutes, flipping halfway through, until the sweet potatoes are tender and golden brown.
- While the sweet potatoes are roasting, prepare the dressing by whisking together olive oil, apple cider vinegar, honey (or maple syrup), Dijon mustard, salt, and pepper in a small bowl.
- In a large bowl, combine the mixed greens, red onion, and toasted pumpkin seeds or walnuts (if using).
- Once the sweet potatoes are roasted and slightly cooled, add them to the salad bowl.
- Drizzle the dressing over the salad and toss gently to combine.
- Sprinkle crumbled feta on top and serve immediately.