Rinse the raw tuna under running water, pat it dry with a paper towel (photo 1) to remove excess moisture, and cut it into 3 cm cubes (photo 2). Heat a frying pan with 3-4 tbsp of olive oil and a pinch of dried oregano. Dredge each tuna cube in flour, shaking off the excess (photo 3).
Place the floured tuna pieces into the hot oil with oregano (photo 4). Brown them well on all sides. In a separate frying pan, sauté the onion (photo 5), cut into thin (but not thread-like) half-rings. Add the julienned carrot (photo 6). Sauté the vegetables for about 5 minutes.
Pour 3-4 tbsp of balsamic vinegar into the pan with the onion and carrot. Add a pinch of brown cane sugar. Stir well. Let the vinegar evaporate over medium heat, then add a little water (photo 7). Cover with a lid and simmer for 15-20 minutes.
While the onion and carrot are simmering, cover the browned tuna (photo 8) and let it cook over low heat. Usually, the fish releases enough liquid, so no additional water is needed. Then transfer the tuna to the pan with the softened onion and carrot. Add a little more water, black peppercorns, and cover with a lid. Cook for another 5-10 minutes (photo 9). Taste and adjust salt if necessary, adding more water if needed. Cook the tuna until fully done. Turn off the heat and serve!
Notes
Store the prepared sweet and sour tuna in the refrigerator for up to 3 days in a covered container. Serve with crispy bread.