Freeze the salmon fillet beforehand for easier slicing. Using a very sharp knife, cut into wafer-thin slices and arrange them on a large, flat platter.
Drizzle with the juice from 2 squeezed lemons and refrigerate for 10-15 minutes.
Season with salt to taste, then sprinkle the 2 finely chopped shallots and 2 tablespoons of green pepper on top and pour olive oil evenly over the top.
Garnish with fresh or dried dill if desired and serve immediately.