Preheat oven to 350°. Grease and flour a 10-in. fluted tube pan., Cream butter and brown sugar until light and fluffy, 5-7 minutes. Add 1 egg at a time, beating well after each addition. Beat in vanilla. In another bowl, whisk flour, baking powder and salt; add to creamed mixture alternately with sour cream, beating after each addition just until combined., Transfer to prepared pan. Bake until a toothpick inserted near center comes out clean, 55-65 minutes. Cool in pan 10 minutes before removing to a wire rack to cool completely., For glaze, combine butter and pecans in a small saucepan over medium heat, stirring constantly, until butter is light golden brown, 4-5 minutes. Stir into confectioners' sugar. Add vanilla, salt and enough cream to reach a drizzling consistency. Drizzle glaze over cake, allowing some to drip down sides. Let stand until set.