Position racks in centre and bottom of oven and preheat oven to 250°C (230°C fan-forced). Place 2 large heavy non-stick baking trays in oven to heat.
In a small bowl, mix the ground coriander, cumin, 1½ tsp sea salt flakes and 1 tsp freshly ground black pepper. Coat salmon with 1 tbs oil and season all over with spice mixture.
In a large bowl, toss the baby broccoli with the remaining 1 tbs oil and season with salt and pepper.
Remove preheated trays from oven. Place salmon, skin-side down, on trays. Scatter baby broccoli around salmon. Roast, rotating trays halfway through cooking, for 12-14 mins or until salmon is cooked through with a rosy centre.
While salmon cooks, in a small bowl, whisk yoghurt, lemon rind, 1 tbs lemon juice and chopped dill. Season with salt and pepper. Transfer salmon and baby broccoli to a large platter. Spoon over yoghurt sauce and sprinkle with sesame seeds, coriander sprigs and dill sprigs.