In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
In a medium bowl, whisk together the melted butter, buttermilk, eggs, and vanilla. Mash the banana well and stir it in.
Add the liquid ingredients to the dry and stir just until combined. Stir in the macadamia nuts.
Heat a large nonstick skillet or griddle over medium heat. Grease well with butter or vegetable oil.
Use a 1/4 cup measuring cup to form pancakes. Cook until bubbles form on top. Flip over and continue to cook until cooked through. Turn down the heat some if they start to get too browned before they are set.