Preheat oven to 350 degrees. Bake 1/2 cups pecans in a single layer in a shallow pan 6-8 minutes or until toasted and fragrant, stirring after 4 minutes.
Beat sour cream and next 3 ingredients at low speed with an electric mixer 2 minutes or until blended.
Stir together flour and next 3 ingredients. Add to sour cream mixture, beating just until blended. Stir in apples and 1/2 cup toated pecans. Spoon batter into a greased and floured 9x5 inch loaf pan. Sprinkle with remaining 1 cup chopped pecans; lightly press pecans into the batter.
Bake at 350 degrees for 1 hour to 1 hour and 5 minutes or until a wooden pick inserted into the center comes out clean, shielding with aluminum foil after 50 minutes to prevent excessive browning. Cool in pan on wire rack for 10 minutes. Remove from pan to wire rack.
Bring butter and brown sugar to a boil in a 1 quart heavy saucepan over medium heat, stirring constantly; boil 1 minute. Remove from heat and spoon over top of bread; let cool completely (about 1 hour).