Cinnamon-Walnut Bundt Cake

Ingredients

• 1/2 cup packed light brown sugar
• 2 1/2 teaspoons ground cinnamon
• 1/2 cup walnuts, coarsely chopped
• 3 cups cake flour
• 1/4 teaspoon baking soda
• 1/4 teaspoon baking powder
• 2 1/2 sticks (10 ounces) unsalted butter
• 2 3/4 cups granulated sugar
• 1 teaspoon kosher salt
• 1 tablespoon vanilla extract
• 6 large eggs
• 3/4 cup sour cream
• 2 tablespoons unsalted butter (1/4 stick)
• 2 tablespoons water
• 1/4 cup light rum
• 1/2 cup powdered sugar