Preheat oven 180°C. Spray a large fluted cake ring with nonstick baking spray.
In a small bowl, combine brown sugar, pecans, and 1 tsp cinnamon; set aside.
In a large bowl, combine sugar and butter. Beat at medium speed with an electric mixer until creamy. Add eggs, one at a time, beating well after each addition. Stir in sour cream, kumara, and vanilla.
In a medium bowl, combine flour, baking soda, remaining 1 tsp cinnamon, salt, and nutmeg. Gradually add to the butter mixture, stirring well.
Pour half of the kumara batter into prepared tin. Sprinkle evenly with brown sugar mixture. Spoon remaining batter evenly over brown sugar mixture. Bake for 1½ hour, or until a wooden pick inserted in center comes out clean.
Cool in pan for 10 minutes. Remove from pan, and cool completely on a wire rack. Top with Rum Glaze and chopped pecans.
Rum Glaze:2 cups icing sugar
½ cup cream
¾ tsp rum essence (or ¼ tsp rum)
In a small bowl, whisk together icing sugar, cream, rum or essence until smooth, drizzle over cooled cake.