Combine buttermilk and cornmeal in a medium bowl.

Let the mixture rest for 1 hour at room temperature (or up to one day) to soften the cornmeal.

Place an empty cast-iron skillet on the top rack of your oven.

Preheat oven and skillet to 425°F.

In a small bowl, combine flour, baking powder, and salt.

Mix well the flour mixture.

In a separate bowl, beat the eggs and maple syrup.

Add the egg mixture to the buttermilk and cornmeal mixture.

Add the dry ingredients to the wet ingredients and stir only until moistened.

Carefully remove the hot skillet from the oven.

Place the cold butter into the hot pan.

Immediately return the pan to the oven until the butter has melted.

Remove the skillet from the oven and pour the melted butter into the bowl containing the batter.

Stir to combine, then pour the batter into the hot skillet.

Immediately place the skillet back into the oven.

Bake for 15-25 minutes, or until lightly browned and a toothpick inserted into the center comes out clean.

Serve warm.