The trick is to a really fabulous cornbread is to make it in a cast-iron skillet and get the skillet screaming hot before you pour in the batter. If you don't have a cast-iron skillet, use an 8x8 ovenproof baking dish.
Preheat the oven to 450 degrees. When the oven reaches temperature, add the oil to the cast-iron skillet, place it in the oven and let it get hot, about 10 minutes.
In a bowl, add the cornmeal, salt and baking soda and blend well to combine. Then add the okra, red onion, corn, jalapeno, banana pepper and poblano pepper and toss to coat. Set aside.
In a large glass measuring cup, crack the egg and beat lightly. Then add the buttermilk and whisk to combine.
Pour the wet ingredients with the dry and fold gently so everything comes together.
Remove the heated skillet and carefully pour the batter in. The batter should sizzle and bubble and this is what is going to make a crispy crust. Place the skillet back into the oven and let it cook until golden, about 35 minutes. Remove to a rack and let cook slightly...if you cut into it immediately, it will fall apart, so be patient and wait 10 minutes.
Using a serrated knife, cut into 8 wedges and serve warm with butter.
Keep any leftover cornbread in the fridge and serve toasted for breakfast with eggs and sausage or ham or whatever you like.