Preheat your oven to 350 degrees F (175 degrees C).
In a heavy cast-iron pan on low heat, melt the Butter (1/2 cup) on the stove top, then add in the Jalapeño Pepper (1/2) and cook for about a minute. The goal is to soften the diced pepper and flavor the butter with the slight kick.
Allow the butter to cool a bit, then add it to a large bowl along with the Buttermilk (1 cup), Granulated Sugar (1/2 cup), and Egg (2). Using a whisk, give it a go until it was relatively smooth and no gritty bits from the sugar are visible.
In another bowl, combine the Cornmeal (1 1/4 cup), All-Purpose Flour (3/4 cup), Baking Soda (1/2 teaspoon), and Salt (1/2 teaspoon). Then add it all to the bowl with the wet ingredients and combine. Try to not over-work the batter.
Since you will be using the same cast-iron pan to bake the corn bread and it is already greased from the butter earlier, pour in the cornbread batter and level off. Then into the preheated oven on the middle rack for about 30-35 minutes. If you’re not using a cast iron pan, you ca use an 8x8 baking dish greased.
Stick a toothpick in the center and if it comes out clean, you’re ready to enjoy! Allow it to cool a bit before using an offset spatula to gently work the edges before removing it out on the pan.