Put the capers, anchovies into a mortar and, using a pestle, mash it into a coarse paste. Add the olive oil, lemon zest & juice.
Deseed the chilli and remove the veins if you don’t want the stuffing spicy, then finely chop the flesh.
Add the chilli to paste, together with the olive slices and dill.
Squash and mix everything together with the pestle - you should get a coarse, bitty paste.
Place the salmon skin-side down in the middle of a roasting tray. Make deep cuts into the flesh at 3cm intervals, using a sharp knife. Put some stuffing into each cut. Sprinkle any excess paste around the salmon.
Cover and refrigerate for at least 2 hours, preferably overnight.
Preheat the oven to 180°C. Put the tray with the salmon in the middle of the oven and roast for 20 minutes.
Rest for 5 minutes, then serve.