Mix the flour, baking powder, sugar and salt. Add the vegan butter in small pieces and mix everything roughly into a crumble. Then add the soy milk and knead everything - only as long as necessary - into a dough. Finely dice the rhubarb, add to the dough and knead again briefly.
Roll out the dough on a floured work surface to about 2.5 cm thick. Using a cookie cutter or a glass, cut out 4 round dough patties, each 7-8 cm in diameter. Form a fifth scone from the leftover dough with your hands.
Preheat the oven to 220 degrees Celsius. Place the scones on a baking tray covered with baking paper, brush with a little soy milk and bake for about 15 minutes.
Serve the scones with some vegan creme fraiche and jam.
Notes
If you want to enjoy the scones as a dessert without toppings, you can simply increase the amount of sugar, for example double it.