01 - Set oven to 400°F. Line a baking tray with parchment paper.
02 - In a large bowl, combine sweet potato cubes and red onion slices with 1 tablespoon olive oil, ground cumin, smoked paprika, salt, and pepper. Toss to coat evenly.
03 - Spread the seasoned vegetables evenly on the baking tray. Roast for 25 to 30 minutes, turning once halfway through, until sweet potatoes are tender and golden. Remove from oven and allow to cool slightly.
04 - Whisk together remaining olive oil, balsamic vinegar, Dijon mustard, honey, salt, and pepper in a small bowl or jar until well combined.
05 - In a large bowl, combine baby spinach, sliced cucumber, diced avocado if using, and roasted sweet potatoes with onions.
06 - Drizzle the dressing over the salad ingredients and toss gently to distribute evenly.
07 - Sprinkle crumbled feta cheese and toasted pumpkin seeds or walnuts on top before serving.