In a mixing bowl, whisk together the buckwheat flour, sugar, baking powder, baking soda and salt.
In another bowl, whisk together the buttermilk, vanilla extract, melted coconut oil and egg. Pour the liquid mixture into the flour mixture, add in ¾ cup fresh blueberries and stir everything together. Let the batter rest for 10 minutes while you preheat your waffle iron.
Pour the batter into your waffle iron and cook until golden brown and slightly crispy. Repeat with remaining batter.
For the blueberry sauce: Add 1 cup fresh blueberries in a saucepan with a splash of water and bring to a simmer. Stir often until the blueberries burst and a sauce forms. Sweetener with sugar or honey, if desired.