Mix the rhubarb with half of the sugar. Place the flour in a bowl and mix with all the other ingredients up to and including the vanilla seeds. Add the butter and rub together using your hands to form an even, crumbly mixture. Add the rhubarb. Pour in the milk and mix quickly to create a soft dough – do not knead. Flatten the dough, cover and chill for approx. 30 mins.
Divide the dough in half, roll out each half to approx. 2 cm thick (approx. 16 cm in diameter). Cut each half into eight pieces, place the scones on a baking tray lined with baking paper, brush with milk. Bake for approx. 25 mins. in the centre of an oven preheated to 200°C. Remove from the oven and allow to cool a little on a rack.
Ca. 25 Min. in der Mitte des auf 200 °C vorgeheizten Ofens, auf einem Gitter etwas abkühlen.
Whisk the ricotta, cream, sugar and lemon zest until creamy. Serve with the scones.