Place noodles in a large bowl and cover with boiling water. Allow to soak for around 5 minutes or until completely softened. Drain noodles and set aside in a colander.
Heat butter in a large frying pan on medium-high heat. Season steak with salt and pepper and add to hot pan. Cook for 2-3 minutes on each side for medium-rare and remove from pan. Allow to rest for 5-10 minutes before slicing.
Meanwhile, for the dressing, combine lime juice, soy sauce, garlic, chilli flakes and oil in a small bowl and whisk to combine.
To assemble, add noodles, tomatoes, cucumber, capsicum and steak to a large salad bowl. Pour over dressing and toss to combine. Divide between 4 serving bowls and top each one with sesame seeds and pine nuts. Serve.