Preheat oven: Set oven to 350°F (175°C). Grease or line an 8x8 inch baking dish.
Mix ingredients: In a large bowl, combine Jiffy mix, sour cream, eggs, melted butter, sugar (if using), and salt. Stir until just combined.
Avoid overmixing: Mix gently. The batter should be smooth but not overworked.
Pour into pan: Spread batter evenly in the prepared dish.
Bake: Bake for 25–30 minutes, or until golden brown and a toothpick comes out clean.
Rest and serve: Let cornbread cool for 5 minutes before slicing. Serve warm with butter or honey.