Preheat the oven to 180°C (350°F) and grease a 23cm (9 inch) springform pan with coconut oil. Set aside.
In a large bowl, sift together the spelt flour, almond flour, baking power, baking soda, and salt. Set aside.
225 grams (1 ½ cup) light spelt flour, 100 grams (1 cup) almond flour, 2 teaspoons baking powder, ½ teaspoon baking soda, ¼ teaspoon sea salt
In a medium bowl, whisk together the coconut oil and coconut sugar until fully combined and slightly lightened in colour (you can also use electric beaters), about 3-4 minutes. Whisk in the eggs until incorporated, then add the milk, vinegar, and vanilla. Stir to fully combine.
60 grams (¼ cup) coconut oil, 100 grams (½ cup) coconut sugar, 2 large eggs, 120 ml non-dairy milk, 1 teaspoon apple cider vinegar, 1 teaspoon pure vanilla extract*
Add the milk mixture to the larger bowl and whisk gently until just combined. Don't over-mix, spelt is sensitive.
Pour the batter into the prepared pan, then top with the rhubarb in a spiral shape.
2-3 stalks rhubarb
Bake for 35-40 minutes, or until golden and a toothpick inserted in the centre of the cakes comes out clean. Cool for ten minutes in the pan before removing the sides and cooling completely on a rack.
Notes
* Vanilla can be substituted for here with a 1/4 teaspoon of cardamom instead.