Preheat the oven to 375 degrees. Line (2) 12 cup cupcake pans with cupcake liners.
Lightly spoon 2 cups of the flour into dry measuring cups and level with a knife. Add the sugar, baking soda, cinnamon, and salt; stir to combine.
Combine ¾ cup water, ½ cup unsalted butter, and ½ cup unsweetened cocoa powder in a medium saucepan over medium heat. Bring to a boil while stirring frequently.
Add to the flour mixture and mix with an electric mixer at medium speed until well blended. Add the buttermilk, vanilla, eggs and 1 teaspoon of the vanilla; beat well.
Scoop batter into paper lined cupcake pans filling about ¾ full. Bake for 20 minutes or until cupcake bounces back when pressed lightly with finger. Remove from oven and place on cooling rack.
FOR THE ICING
Add the butter, buttermilk, and cocoa powder to a small saucepan. Bring to a boil, stirring constantly.
Remove the chocolate mixture from the heat and gradually add the powdered sugar and remaining vanilla. Stir in pecan pieces.
Spoon frosting over warm cupcakes. Cool completely.