Preheat the oven to 350 degrees.
In a bowl, mix the chopped rhubarb, candied ginger, brown sugar and corn starch and set aside.
Mix the milk and vinegar and set aside to curdle for a couple of minutes.
In the bowl of a stand mixer or a large bowl, using the whisk attachment or a regular whisk, cream together the butter and the sugar until soft and fluffy, about two minutes.
Add the milk-vinegar mixture, sugar, and vanilla extract and mix well.
In another bowl, mix the flour, baking powder, baking soda and salt.
Add the flour mixture to the wet ingredients in three batches, mixing for about 20 seconds after each add, and scraping down the sides and bottom of the bowl with a spatula to ensure even mixing.
Prepare a 10-inch springform pan by greasing the bottom and sides with oil or vegan butter. Cover the bottom with parchment paper which will make for much easier unmolding. Place the springform pan on a cookie sheet to catch any juices from the rhubarb that may leak out as the cake bakes.
Place the chopped rhubarb in the bottom of the pan and spread evenly. You can make a decorative pattern, if you like.
Pour the cake batter on top of the rhubarb and spread evenly. Smooth the top.
Bake for 60 minutes or until a toothpick inserted in the center comes out clean.
Let the cake cool in the pan for 15 minutes. Then invert a dish or a cake stand over the cake pan and carefully but quickly flip the cake. It is important to unmold the cake while it is still warm otherwise the juices will start sticking to the pan.
Open the springform pan and remove. Carefully lift off the bottom and the parchment paper.
Garnish, if you like, with more strips of candied ginger. Et voila!