01 - 
                Whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg in a medium bowl until evenly mixed.
              
              
              
                02 - 
                Beat softened unsalted butter with granulated sugar at medium-high speed for 2 to 3 minutes until pale and fluffy.
              
              
              
                03 - 
                Incorporate eggs one at a time, beating well after each addition, then stir in vanilla extract, scraping the bowl as needed.
              
              
              
                04 - 
                Blend sour cream into the batter until smooth, enhancing moisture and tenderness.
              
              
              
                05 - 
                Gently fold the dry ingredients into the wet mixture until just combined, avoiding overmixing.
              
              
              
                06 - 
                Toss peeled, chopped apples with brown sugar and cinnamon in a small bowl to coat evenly.
              
              
              
                07 - 
                Pour half the batter into a greased loaf pan, spread half the apple mixture evenly, then top with remaining batter and apples. Swirl gently with a knife for a marbled effect.
              
              
              
                08 - 
                Bake at 350°F for 50 to 60 minutes or until a toothpick inserted in the center comes out with moist crumbs. Cool in pan for 10 minutes before transferring to a wire rack.