Toss fennel, celery and parsley with lemon juice and 3 tablespoons olive oil in a large bowl; season with salt and pepper. Set aside.
Season steak with salt. Coat a skillet with a bit of cooking oil and put over high heat. Add the steak and cook for 3-5 minutes per side until cooked to your desired level of doneness. Set the steak on a cutting board to rest. Slice the steak against the grain into ¼-inch slices. Divide the steak between two plates and top with the salad.