Preheat the oven to 425 degrees F. Lightly coat a large baking sheet with cooking spray.
In a bowl, toss the sweet potatoes with 3 teaspoons olive oil, maple syrup, cinnamon, ½ teaspoon salt and cayenne. Transfer to the prepared baking sheet and spread in a single layer.
In a separate bowl, toss the red onion pieces with 1 teaspoon olive oil and ⅛ teaspoon salt. Scatter the red onion pieces between the sweet potatoes so that they’re all in a single layer.
Roast for 20 minutes. Using a spatula, flip and stir the sweet potatoes and onions. Return to the oven, placing them on the bottom rack. Roast until the sweet potatoes are tender and browning on the bottom side, about 10 additional minutes.
Remove from the oven and cool to room temperature.
Place the mixed greens in a large serving bowl. Toss with 3 tablespoons of the dressing. Top with the roasted sweet potatoes and onions, chickpeas, dried tart cherries and slivered almonds.
Drizzle with the remaining 1 tablespoon of tart cherry dressing. Serve.