Combine the butter and sugar together with a fork or beater until smooth. Mix in flour and cornmeal, adding baking powder and salt. Whisk milk and eggs into the dry mixture. Finally, fold in the jalapeño.
Put mixture into a cast iron skillet, greased muffin tin, or baking sheet. Place in oven and cook for 25-30 minutes, or until golden brown. Let cool for 5-10 minutes, serve, and enjoy!