Preheat the oven to 150°C and line a baking tray with greaseproof paper.
Mix the flour, sugar, and baking powder in a bowl until combined.
Whisk in the eggs gradually until the mixture forms a dough.
Mix in the cherries, hazelnuts, and lemon zest.
Divide the dough into six portions and roll each into a sausage shape 3cm in diameter.
Flatten the dough slightly and place on the tray with 6cm gaps between them.
Bake for 15-20 minutes until pale golden-brown then cool for 10 minutes.
Cut diagonal slices 5cm thick and arrange them back on the tray.
Bake for 6-8 minutes, turn over, and bake for another 6-8 minutes until crisp.
Cool the biscotti on a wire rack.