In a large bowl, sift together the flour, cornmeal, sugar, baking powder, baking soda, and salt. Whisk together the buttermilk, eggs, and melted butter in a bowl or liquid measuring cup. Add the buttermilk mixture to the dry ingredients and whisk just until combined.

Preheat the oven to 300°F. Heat a large, heavy-bottomed skillet over medium heat and lightly coat with canola oil. Ladle ¼ cup batter into the pan for each pancake, cooking only a few at a time. Cook until the bubbles on the top burst and the bottoms are golden brown, about 1½ minutes.

Flip the pancakes and cook until golden, about 1 minute. Transfer to a baking sheet and place in the oven to keep warm. Repeat with the remaining batter, adding more oil to the pan as necessary. Transfer to warmed serving plates. Serve hot or warm with maple syrup.