Grate or pare the zest from the lime and juice it. Add to a bowl. Measure out 1 tbsp of the tamari and whisk with the lime juice. Peel and finely slice the onion. Add to the bowl and leave to marinate.
Peel and grate the ginger. Mix in a seperate bowl with 1 tbsp oil. Add the beef and season. Set to one side to marinate.
Halve the melon. Scoop out the seeds. Slice away the skin. Finely chop the melon into thin slices. Pop in a large bowl.
Finely shred half of the cabbage. Add to the melon. Pick the leaves off the coriander and mint sprigs. Add them to the melon. Halve the pepper, scoop out the seeds and finely slice it.
Warm a dry frying pan over a medium heat. Add the sesame seeds. Toast for 1-2 mins till they’re golden and nutty. Shake the pan a few times to stop them catching and burning. Scatter over the melon.
Pour the onions and dressing over the salad. Toss to make sure everything is coated in the dressing. Put to one side while you cook the beef.
Put the frying pan back on the heat. When it’s hot, add the beef. Fry for 3-5 mins. Turn every so often till it’s browned all over.
Divide the melon salad between two plates. Top with the beef and serve straight away.