Preheat oven to 350°. Grease and flour 9x5 inch loaf pan.
Bake 1/2 cup pecans in a single layer in a shallow pan 6-8 minutes or until toasted and fragrant, stirring after 4 minutes. Chop toasted pecans and set aside.
Beat sour cream and next 3 ingredients at low speed with an electric mixer 2 minutes or until blended.
Stir together flour and the next 3 ingredients. Add to sour cream mixture, beating just until blended. Stir in apples and 1/2 cup toasted pecans.
Spoon batter into prepared pan. Chop remaining pecans and sprinkle on top of batter; lightly press pecans into batter. Bake at 350° for 60-65 minutes or until wooden pick inserted into center comes out clean. Cover with aluminum foil after 50 minutes to prevent excessive browning.
Cool in pan on a wire rack 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.
NOTE: To freeze, cool bread completely; wrap in plastic wrap, then in aluminum foil. Freeze up to 3 months. Thaw at room temperature.