Pull and trim the white lining off of the kidney, then cut the kidney into 1-inch cubes. Season with pepper and salt, and dredge well with flour.
In a pan set to high heat, begin heating the olive oil. When the oil is hot, add the kidney cubes and fry until cooked through. Remove the kidney from the pan.
In the same pan, add the butter, garlic, coriander, and cook until garlic turns light brown. Add the kidney back in, and then add the lemon juice. Let cook for 30 more seconds, and finish with a liberal sprinkle of salt and pepper.