Juice half of the lemon and slice the remaining into thin rounds for garnish. Mince the parsley.

Pat the yellowtail fillets dry with paper towels, season with salt and pepper, and coat with flour.

Heat olive oil in a pan over medium heat. Place the fillets skin-side down and cook for 2 minutes until golden. Flip and cook for another 2 minutes. Remove from the pan.

Clean the pan and add lemon juice, parsley, butter, and soy sauce. Heat over medium-low until bubbling and thickened.