Preheat oven to 350 degrees F.
Melt butter in a nonstick pan over medium heat. Brown butter until golden and toasty, about 3-5 minutes. Remove from heat and add maple syrup.
Sift together flour with granulated sugar, salt, baking powder, cinnamon and nutmeg in a medium bowl. Add eggs one at a time, whisking until well combined.
Add orange zest, vanilla, pumpkin puree and melted butter mixture. Whisk until fully incorporated. Cover with plastic wrap and chill for at least 30 minutes and up to overnight.
Spray madeleine pan with cooking spray. Fill molds about ¾ full with batter. Bake for 7-9 minutes or until the center has set and the edges are golden brown. Remove from oven and unmold madeleines. Dust with powdered sugar and serve immediately.