In a large mixing bowl, whisk together the buckwheat flour, sugar (if using), baking powder, baking soda, and salt.
In a separate bowl, mash the ripe banana and add the almond milk, coconut oil, and vanilla extract. Mix well.
Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix; a few lumps are okay.
Let the batter rest for a few minutes to allow the baking powder to activate.
Heat a non-stick skillet or griddle over medium heat. If needed, lightly grease it with additional coconut oil.
Pour 1/4 cup of batter onto the skillet for each pancake. Cook until bubbles form on the surface, then flip and cook until the other side is golden brown.
Continue until all the batter is used.
Serve the pancakes warm with your favorite toppings, such as sliced bananas, berries, maple syrup, or a sprinkle of nuts.