- Preheat the oven to 375°F. Line the cake pan with parchment paper (or grease & flour), and set aside. 
- Chop the rhubarb into 1 inch slices. Add into a small bowl, with 3 tablespoon sugar, lemon juice and lemon zest. (See notes) 
- Mix the cornstarch and water together, and set aside. 
- In a bowl, mix the flour, baking powder, salt and sugar. 
- In another bowl, mix the oil, non-dairy milk and cornstarch mixture, and mix well. Then add the rhubarb mixture. 
- Add the wet ingredients to the dry ingredients, and mix just until everything is incorporated. Transfer to the pan. If you want, you can add a decoration of rhubarb on top. 
- Bake for 30-40 minutes, or until a toothpick comes out clean (or with a few crumbs). Cool and enjoy!