Make small cuts between the lean and fat parts of the pork loin. Season with salt and pepper, then coat with flour.

Slice the onion thinly.

Heat vegetable oil in a pan over medium-high heat. Add the pork and cook until browned. Flip, cover, and cook on low heat for about 5 minutes until fully cooked. Slice into serving pieces and plate.

Using the same pan, sauté the onion over medium heat until softened. Add the remaining sauce ingredients and simmer until the liquid reduces by half.