Heat 1 tbsp oil in skillet over medium heat. Season the pork with the curry, 1/2 tsp salt and 1/4 tsp pepper. Cook until browned and cooked through 6-8 minutes per side.
Heat the remaining 2 tbsp oil in a second skillet over medium heat. Add the onion and cook, covered, stirring occasionally, for 5 minutes.
Add the cabbage, vinegar, 2 tbsp water, 3/4 tsp salt and 1/4 tsp pepper, and apple, if using. Cook, covered, stirring occasionally, until the cabbage is just tender, 5 to 6 minutes. Fold in the dill and serve with pork.