Preheat oven to 425ºF. Line a small baking sheet or plate with parchment paper.

Combine pecans, ¼ cup maple syrup, ¼ tsp. salt, ¼ tsp. cinnamon, and cayenne in a small saucepan. Cook mixture over medium-high until bubbly and thickened, about 4 to 5 minutes. Pour onto parchment paper and spread in an even layer. Allow mixture to cool completely while you prepare remainder of recipe.

Toss sweet potatoes and shallots with olive oil and remaining ½ tsp. salt. Spread evenly on a large rimmed baking sheet, avoiding too much overlap, if possible. Bake until sweet potatoes are almost tender, about 15 minutes.

Meanwhile, microwave butter in a small bowl until melted. Stir in remaining 2 Tbsp. maple syrup and ¼ tsp. cinnamon. Remove sweet potatoes from oven and brush with maple butter. Flip the sweet potato slices over, then brush the other side with remaining maple butter. Place back in the oven for 10 more minutes, until browned and caramelized.

Transfer roasted sweet potatoes and shallots to a serving platter and scatter pecan praline mixture overtop. Garnish with orange or lime zest, if desired.