Preheat your oven to 400°F (200°C). Place a 10-inch cast iron skillet in the oven to heat up as the oven warms.
In a large mixing bowl, whisk together the cornmeal, all-purpose flour, baking powder, salt, baking soda, and sugar until well combined.
In another bowl, whisk together the buttermilk, melted butter, and beaten eggs until smooth.
Pour the wet mixture into the dry ingredients. Stir gently until just combined; do not overmix. Fold in the shredded cheddar cheese, diced jalapeño, and sliced green onions.
Carefully remove the hot skillet from the oven. Add a tablespoon of butter to the skillet and swirl it around to grease the bottom and sides effectively.
Immediately pour the cornbread batter into the hot skillet. Spread it out evenly with a spatula.
Place the skillet back in the oven and bake for 20-25 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Once baked, allow the cornbread to cool for about 5-10 minutes in the skillet. Cut into wedges and serve warm with butter or your favorite honey for a delightful finish.
Notes
For less heat, remove the seeds from the jalapeño.