How to Make It
Heat 1/4 cup butter in a large, high-sided skillet over medium. Add onions, and cook, stirring often, until tender and translucent, 10 to 12 minutes. Add cabbage, and cook, stirring often, until slightly wilted, 5 to 7 minutes. Stir in vinegar and sugar. Reduce heat to medium-low. Cover and cook, stirring occasionally, until cabbage is tender, 35 to 45 minutes. Add red currant jelly, salt, and remaining 1/4 cup butter; stir until jelly and butter have melted. Serve hot.