Preheat the oven to 350°F. Line a 9x5-inch rectangular loaf pan with parchment paper, leaving a 2-inch overhang on opposite ends along the length and brush olive oil on exposed sides.
In a medium bowl, whisk together both flours, baking powder, baking soda, cinnamon, nutmeg and salt.
In a separate large bowl, whisk together mashed banana with brown sugar until well blended. Add egg, buttermilk or plain yogurt, vegetable oil and vanilla extract and beat until well combined and smooth. Gently mix in dry ingredients and then fold in the chocolate chips and macadamia nuts just before all of the flour is incorporated. Be careful not to over mix the batter - a few small lumps is OK.
Pour batter into the prepared pan and smooth the top. Bake for 45-55 minutes until evenly browned and slightly cracked at the surface. Transfer to a wire rack to cool.