Preheat oven to 350 degrees. Grease and flour bundt pan. (at least a 10 cup bundt pan)
Whisk together cake mix, brown sugar, cinnamon and nutmeg in large bowl of mixer. Make a "well"; add oil, sour cream, eggs and pumpkin. Blend on low speed for about 30 seconds. Beat at medium speed for 2 minutes. Stir in raisins.
Pour 1/2 of batter into a prepared bundt pan. Sprinkle filling evenly over batter. Pour remaining batter on top.
Bake for 1 hour or until cake tested inserted in center comes out clean. Remove from oven and let cool on rack for 10 to 15 minutes. Invert onto large plate; cool completely and then glaze. For best results, let cake sit over night before diving in!
FILLING: Mix well; set aside until ready to use.
GLAZE: Brown butter in sauce pan over medium heat just until a deep golden brown. Watch closely as the butter can burn quickly. Remove from heat once you've reached desired color.
Stir in brown sugar and buttermilk and return to heat; reduce heat. Stir until sugar is completely dissolved and no longer grainy. Stir in maple and vanilla; set aside to cool.
Add powered sugar; stir until creamy. If glaze seems too thick, add additonal buttermilk or milk until desired consistency.