Peel sweet potatoes and cut into ¾-inch cubes, keeping pieces as uniform as possible for even cooking.
2 pounds sweet potatoes
In a large bowl, combine sweet potato cubes, oil (or melted butter), brown sugar, cinnamon, salt, garlic powder, and nutmeg. Toss until all cubes are evenly coated.
2 tablespoons melted butter or olive oil, 1 tablespoon light brown sugar, 1 teaspoon ground cinnamon, 1/2 teaspoon kosher salt, 1/4 teaspoon garlic powder, 1/4 teaspoon ground nutmeg
Preheat air fryer to 400°F for 3-4 minutes.
Working in batches if needed, arrange sweet potato chunks in a single layer in the air fryer basket. Don't overcrowd.
Cook at 400°F for 12-15 minutes total, shaking the basket halfway through (around the 6-7 minute mark). They're done when fork-tender inside with golden, caramelized edges.
Pierce a cube with a fork. It should slide in easily. If they need more time, cook in 2-minute increments.
While sweet potatoes are cooking, toast pecans in a dry skillet over medium heat for 3-4 minutes, stirring frequently, until fragrant and lightly golden. Let cool slightly, then chop.
In a small bowl, combine the toasted pecans, melted butter, brown sugar, and cinnamon. Stir until pecans are well-coated.
1/3 cup chopped pecans, 3 tablespoons melted butter, 2 tablespoons light brown sugar, 1/2 teaspoon ground cinnamon
Transfer hot sweet potato cubes to a large serving bowl. Pour the pecan-butter mixture over the top and toss gently to coat.
Sprinkle with a pinch of flaky sea salt over the top.
Pinch of flaky sea salt
Serve immediately while everything is hot and the butter is glossy.