Step 1: Roast the Sweet Potatoes

1. Preheat your oven to 400°F (200°C).
2. Toss the cubed sweet potatoes with olive oil, salt, and pepper.
3. Spread the sweet potatoes on a baking sheet in a single layer.
4. Roast for 25-30 minutes, or until they are tender and lightly browned, flipping halfway through for even cooking.

Step 2: Toast the Pecans

1. While the sweet potatoes are roasting, heat a dry skillet over medium heat.
2. Add the chopped pecans and toast for 3-4 minutes, stirring frequently to prevent burning.
3. Once the pecans are fragrant and lightly browned, remove them from the pan and set aside.

Step 3: Prepare the Sage Butter

1. In the same skillet, melt the butter over medium heat.
2. Add the chopped sage leaves and cook until the butter starts to brown and the sage becomes crispy, about 2-3 minutes.
3. Stir in the maple syrup and apple cider vinegar, and mix well. Remove from heat.

Step 4: Assemble the Salad

1. In a large bowl, add the fresh spinach and roasted sweet potatoes.
2. Pour the warm sage butter dressing over the salad and gently toss to combine.
3. Add the toasted pecans and sliced red onion, if using.

Step 5: Serve

1. Transfer the salad to a serving platter.
2. Sprinkle crumbled feta cheese on top (optional) for a creamy, tangy finish.
3. Serve warm and enjoy!