Heat oven to 200C/180C fan/gas 6.
Put the potatoes in a large baking tray
and toss with the olive oil and fennel
seeds. Season, arrange in a single layer,
then bake for 20 mins until softened
and starting to crisp.
Turn the potatoes over and add the
beetroot, season and return to the
oven for 15 mins. Place the fish in the
centre, season well and rub over a
little oil from the tray. Return to the
oven for 10 mins more.
Meanwhile, sprinkle the lemon zest
over the crème fraîche with a good
grind of black pepper. To serve, scatter
the fish with basil and dollop with some
of the lemony crème fraîche.