Spray a square 8x8" pan with cooking spray. Preheat your oven to 350°.
Melt the butter in a non stick skillet over medium high heat. Add the diced jalapenos, red pepper, and corn. Cook and stir for 3-5 minutes, or until the veggies start to brown. Remove them to a plate to cool.
In a large mixing bowl, whisk together the flour, cornmeal, sugar, baking powder, and salt.
Add the buttermilk, eggs, vegetable oil, and cooled sauteed vegetables. Whisk together until smooth.
Spread batter in the prepared pan. Bake at 350 degrees for about 40 minutes. Cornbread is done when the edges are golden brown and a toothpick inserted in the center comes out clean. (Moist crumbs are fine.)
Cut warm cornbread into squares and serve with butter or honey butter.
Notes
If you want cornbread that isn't quite as thick, you can bake it in a greased 9x13" pan for 25-30 minutes.
For a mild cornbread, remove the jalapeno seeds and membranes. Leave them in for more heat.