Step 1 (5 minutes): Thinly slice the red cabbage. Mince the onion and garlic. Pat the mackerel fillets dry with paper towels and season them generously with salt and pepper on both sides.

Step 2 (10 minutes): Heat 10 ml of olive oil in a large skillet or pot over medium heat. Add the minced onion and sauté for 3-4 minutes until softened. Add the minced garlic and caraway seeds, cook for another 1 minute until fragrant. Add the sliced red cabbage, apple cider vinegar, and vegetable broth. Stir well, cover, and braise for 5-7 minutes, stirring occasionally, until the cabbage is tender-crisp.

Step 3 (8 minutes): While the cabbage braises, heat another 10 ml of olive oil in a separate non-stick pan over medium-high heat. Once hot, place the mackerel fillets skin-side down in the pan. Sear for 3-4 minutes until the skin is crispy and golden. Flip the fillets and cook for another 2-3 minutes, or until cooked through and flaky. The total cooking time for the fish should be 5-7 minutes depending on thickness.

Step 4 (1 minute): Taste the braised cabbage and adjust seasoning if needed. Serve the pan-seared mackerel fillets immediately alongside the braised red cabbage.