01 - Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, allowing overhang for easy removal.
02 - Whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg in a medium bowl.
03 - Whisk brown sugar, granulated sugar, eggs, oil, and vanilla in a large bowl until smooth. Fold in grated carrots, pineapple, and nuts.
04 - Add dry ingredients to wet mixture; stir until just combined. Set aside.
05 - Beat cream cheese until smooth. Add sugar, egg, and vanilla; blend until creamy and lump-free.
06 - Spread 2/3 of carrot cake batter into prepared pan. Pour cream cheese mixture evenly over top. Dollop remaining carrot cake batter over cream cheese layer.
07 - Use knife or skewer to gently swirl batters together for marbled effect.
08 - Bake for 38-42 minutes until toothpick inserted in center comes out mostly clean.
09 - Cool completely in pan. Refrigerate 2 hours for easier slicing. Cut into bars and serve.