In a large bowl, combine the flour, sugar, baking powder, garlic powder, onion powder, salt, and cayenne pepper if using.
In a separate bowl, beat the egg, butter, and milk together. Add this mixture to the dry ingredients and stir until just combined.
Fold the corn kernels, green onion, and jalapeño into the batter, making sure they are evenly distributed.
Heat a large skillet over medium heat and add enough vegetable oil to cover the bottom.
Once hot, drop spoonfuls of the batter into the skillet. Flatten slightly with the back of the spoon. Cook for 2-4 minutes on each side or until golden brown.
Drain on paper towels. Serve warm with sour cream and green onions sprinkled on top.