Toast the bread and put 2 slices
on each plate. Mash the avocado
with half the lemon juice and season
well. Spread the avocado over each
slice of toast, then lay the beetroot
and salmon on top.
In a small bowl, mix the remaining
lemon juice with the crème fraîche
and horseradish. Season and mix
well to combine. Drizzle over the
open-faced sandwiches. Top each
slice of toast with a few onion slices
and some chopped dill, and serve.