Grease and line an 8" high sided tin and pre-heat oven to 160C.
To prepare the rhubarb, place the butter and sugar into a saucepan and heat until the sugar dissolves and it begins to turn into a syrup.
Meanwhile, cut the rhubarb in half lengthways and trim to size of tin.
Pour the syrup into the tin and arrange the rhubarb so that it covers the base.
To make the cake, beat together the butter and sugar until light and pale. Individually add the eggs, combining well between each addition before adding the vanilla and sour cream and fully incorporating.
Sift in the flour, baking powder and salt and fold until just combined.
Pour the batter onto the rhubarb, level and bake for 40-45mins or until a skewer comes out clean. Once baked, remove from the oven and allow to stand for 5mins before removing from the tin.
Meanwhile, to make the crème anglaise heat the milk in a large saucepan until simmering. Add the remaining ingredients in a mixing bowl and whisk until pale. Once simmering, slowly pour the milk into the bowl, whisking well. Transfer back into the saucepan and heat until thickened, whisking constantly.
To serve, slice a piece of cake and drizzle over the crème anglaise.
