Heat the oven to 400°F (200°C). Place a 9-inch cast-iron skillet or 8–9 inch square baking pan in the oven to preheat. A hot pan helps create crisp edges.

Combine the dry ingredients. In a large bowl, whisk together the cornmeal, flour, sugar, baking powder, baking soda, and salt until evenly blended.

Mix the wet ingredients. In a separate bowl or large measuring cup, whisk the buttermilk and eggs until smooth. Slowly whisk in the melted butter. (If the butter starts to clump, your buttermilk was too cold—no worries, it will still bake up fine.)

Bring it together. Pour the wet mixture into the dry ingredients. Stir gently with a spatula until just combined. A few small lumps are okay. Do not overmix—that can make the crumb tough.

Add extras if using. Fold in corn, cheese, scallions, or jalapeño now. Spread the batter evenly; it will be thick but spreadable.

Grease the hot pan. Carefully remove the preheated pan from the oven. Swirl in a teaspoon of butter or lightly brush oil to coat the bottom and sides.

Bake. Pour the batter into the hot pan and smooth the top. Bake for 18–22 minutes, until the top is golden and a toothpick inserted in the center comes out clean or with a few moist crumbs.

Cool briefly and serve. Let the cornbread rest for 10 minutes before slicing. Serve warm with butter, honey, or your favorite toppings.