Knead spelt flour, raw cane sugar, cinnamon, bourbon vanilla, salt, butter, egg and water into a dough. Shape the dough into a ball and place in the refrigerator for about an hour, wrapped in plastic wrap.
In the meantime, preheat the oven to 200 degrees Celsius top and bottom heat. Wash the rhubarb and cut into one centimetre diamonds. Cut half of the rhubarb from the left, the other half from the right, so that the rhombs fit together. Place in a bowl and gently mix with the starch and maple syrup.
Take the dough out of the fridge and roll it out round on a floured work surface. You are welcome to give the galette a more rustic look. Place the dough on a baking sheet lined with parchment paper and sprinkle with the grated nuts.
If you are motivated, you can arrange the rhubarb pieces in a diamond pattern in the centre of the galette, leaving about four centimetres to the edge. Then fold the edge over the rhubarb pieces, spread some whipped cream on top. Then sprinkle everything with flaked almonds and a little sugar.
Bake the galette for about 45 minutes and enjoy it lukewarm shortly after. A little whipped cream, refined with cinnamon or vanilla, goes wonderfully with it. Or, especially in summer, a scoop of ice cream.