Prepare the quinoa according to the packet instructions, then squeeze over the juice of half a lemon. Season with a good pinch of sea salt and black pepper, then set aside.
Preheat a griddle pan to high.
Slice the courgettes lengthways into thin strips. Griddle the courgette strips for 2 minutes each side and put aside on a plate. Turn the griddle down to a medium heat.
Using a mandolin (use the guard!) or speed-peeler, slice the fennel into thin strips, place in a bowl and squeeze over the juice of half a lemon. Pick and finely chop the herb leaves, stir through the quinoa and season.
Make a dressing by squeezing the remaining lemon juice into a small bowl, then add the yoghurt and 2 tablespoons of oil, and stir to combine. Season with salt and pepper to taste.
Season and rub a little oil all over the salmon fillets, then cook on the hot griddle for 3 to 4 minutes each side, or until the fish is cooked through.
Pile the quinoa on a plate and arrange the griddled courgette and lemony fennel on top, along with flakes of salmon. Dot over the yoghurty dressing, scatter over the remaining herbs, then serve.