Zest half of the lime, then cut it in half and juice one of the halves. Cut the other half into 2 wedges.
Layer the ramen and seasoning, onion, sriracha, soy sauce, fish sauce, kale, lime zest and juice, ginger and steak in a large heatproof soup bowl. Pour the boiling water into the bowl and let it sit undisturbed for 2 minutes. Stir with chopsticks, garnish with the lime wedges and serve immediately.