Mix buckwheat flour, cinnamon, and salt together in a large bowl. Make a well in the center; fill with coconut milk, eggs, honey, 1 tablespoon butter, and baking soda. Mix batter until smooth.
Fold blueberries and banana into the batter; stir gently to combine.
Melt the remaining 1 tablespoon butter on a griddle over medium-low heat. Drop 1/4 cup batter on the griddle; cook until bubbles form and edges are dry, 3 to 4 minutes. Flip and cook until golden brown on the other side, 2 to 3 minutes. Repeat with the remaining batter.