Preheat your oven to 375°F (190°C) and grease your cast iron skillet or baking dish.
In a mixing bowl, combine the cornmeal, flour, baking powder, salt, and cayenne pepper.
In another bowl, whisk together the buttermilk, melted butter, and eggs until well combined.
Slowly incorporate the wet ingredients into the dry ingredients, stirring until they are only just mixed together.
Gently fold in the corn kernels, diced bell peppers, diced green onions, and grated cheddar cheese (if using).
Pour the batter into the greased skillet or baking dish, spreading it evenly.
Place the mixture in the oven that has been preheated and bake for approximately 25-30 minutes. The cornbread should turn a golden brown color and a toothpick inserted into the center should come out clean.
Once done, remove from the oven and allow it to cool slightly before slicing and serving.