Preheat oven to 350°.
Beat softened butter at medium speed with an electric mixer until creamy. Gradually add sugar and beat until fluffy. Add eggs, one at a time, and beat well after each. Mix in vanilla.
In a separate bowl, combine flour, baking powder, and salt. Sift mixture twice.
Add flour mixture to butter mixture, alternating with buttermilk. Begin and end with flour mixture. Fold in chopped pecans.
Combine melted butter and brown sugar. Add cream and stir until smooth.
Pour butter/brown sugar mixture into bottom of 9-inch round cake pan. Arrange pecan halves in butter/brown sugar mixture. Spoon cake batter over pecan halves.
Bake 40-45 minutes, or until a wooden pick inserted in the center comes out clean. Run a knife around the edges of the pan to loosed cake. Turn cake onto serving dish immediately. Serve with Brown Sugar Brandy Sauce, if desired.
Brown Sugar Brandy Sauce
Melt butter over medium heat in a saucepan. Add brown sugar and whisk to combine. Add brandy and whisk to combine. Add cream and whisk until smooth.
Cook, whisking frequently, 2-3 minutes or until sauce is heated through.
Sauce can be made ahead and refrigerated. Reheat in the microwave for serving.