Heat your oven to 200°C/Fan 180°C/Gas 6. Peel and finely slice the onion. Place in a bowl. Zest and juice the lime into the bowl. Add a pinch of salt and scrunch everything together. Set aside to pickle.
Peel and grate the ginger. Place them both in a small bowl. Pour in 2 tbsp tamari, 2 tbsp cold water and 2 tsp oil. Whisk together.
Place the salmon fillets in a small baking dish. Pour over the tamari sauce. Slide the dish into the oven and bake for 15 mins till the salmon is cooked through. It will be dark pink and flake easily when pressed with a fork.
While the salmon cooks, finely slice the spring greens. Peel and grate the garlic.
Heat a deep frying pan or wok. Tip 1 tbsp of the sesame seeds into the pan and toast for 2-3 mins till nutty smelling and golden. Keep shaking the pan while the seeds toast. Transfer to a bowl.
Keep the pan on the heat. Pour in 3 tbsp water. Add the spring greens and the garlic. Cook and stir for 4-5 mins till wilted. Season and take off the heat.
Stir the toasted sesame seeds through the greens. Spoon onto a couple of warm plates and top with the salmon, spooning over any tamari sauce from the dish. Scatter over the pickled pink onions and any marinating liquid.