1. Preheat oven to 350°.
2. Weigh or lightly spoon flours and flaxseed meal into dry measuring cups; level with a knife. Combine flours, flaxseed meal, baking powder, and next 4 ingredients (through salt) in a bowl.
3. Place granulated sugar and sour cream in a large bowl; beat with a mixer at medium speed until blended. Beat in vanilla and eggs. Gradually add flour mixture, beating at low speed until smooth. Stir in apple and pecans.
4. Pour batter into a 9 x 5-inch loaf pan coated with cooking spray. Bake at 350° for 50 minutes until a wooden pick inserted in center comes out clean. Cool 15 minutes in pan on a wire rack; remove from pan.
5. Combine butter and brown sugar in a small saucepan; bring to a boil over medium heat, stirring constantly. Boil 1 minute. Spoon mixture over warm bread. Cool completely on wire rack.