01 - Preheat oven to 425°F. Line a baking tray with parchment paper.
02 - In a large bowl, toss sweet potato cubes with 1 tbsp olive oil, smoked paprika, cumin, salt, and pepper. Spread evenly on the prepared tray.
03 - Roast for 25–30 minutes, tossing halfway through, until sweet potatoes are golden and tender.
04 - In the last 10 minutes of roasting, scatter red onion slices over the sweet potatoes to lightly caramelize.
05 - Meanwhile, whisk together remaining olive oil, maple syrup, Dijon mustard, apple cider vinegar, lemon juice, salt, and black pepper in a small bowl to make the dressing.
06 - In a large salad bowl, combine roasted sweet potatoes and onions, spinach, avocado, nuts, and feta (if using).
07 - Drizzle with dressing and toss gently to combine. Serve warm or at room temperature.