Preheat oven to 400°.
Add flour, oats, baking powder, baking soda, and salt to a medium-sized mixing bowl. Whisk to combine and set aside.
In a larger bowl or a stand mixer, add banana, pineapple, brown sugar, egg, buttermilk, coconut oil, coconut extract, and vanilla. Combine well.
Slowly mix dry ingredients into wet mixture until just combine. Fold in coconut flakes and macadamia nuts.
Prepare a 12 muffin tin by spraying with cooking spray. Spoon batter into muffin cups (fill to top).
Prepare streusel by combining all ingredients in a small bowl. Use fingers or a fork to press and combine ingredints together. Sprinkle about 1 teaspoon streusel on top of each muffin.
Place in oven and bake for 15-20 minutes or until golden brown and a toothpick inserted comes out clean. If muffins get too dark before middles are done, lightly place a sheet of foil on top until they are done. Remove muffins from pan and cool on a wire rack.