Preheat the oven to 350°F. Line a 9”x13” baking pan with parchment paper, or lightly grease with coking spray.
In a large bowl, sift and whisk the flour, granulated sugar, baking powder, baking soda and salt together. In a medium bowl or large glass measuring cup, whisk together the orange juice, plant-based milk, sugar, oil, orange rind, vanilla and almond extracts together.
Make a well in the dry ingredients and pour in the wet ingredients. Mix with a large spoon until combined, taking care not to over-mix. Pour into the prepared baking pan. Bake in the center of the oven for 30-35 minutes or until a toothpick inserted into the middle comes out clean, or with a few baked crumbs. Cool the cake completely before frosting.
For the Blood Orange Frosting:
Whisk the sugar and flour together in a small bowl. Pour in the orange juice slowly, whisking constantly. Pour through a fine mesh sieve into a small pot and place over medium-low heat, stirring constantly. Once the mixture thickens and is bubbling, cook another 2 minutes stirring constantly. Do not under-cook or the frosting will taste like flour and will not thicken enough.
Pour into a bowl and place plastic wrap directly over the surface to prevent a skin from forming. Let cool completely to room temperature.
In a stand-mixer with whisk attachment, beat the vegan butter on high for 5 minutes, scraping down the sides as necessary. Beat in the vanilla extract. Reduce the speed to medium, and add the cooled flour mixture a spoonful at a time. Once it’s all added, beat on high for about 5 minutes or until light, fluffy and silky.
To Assemble the Cake:
Spread the blood orange frosting over the cooled cake. Decorate with blood orange slices, if desired. The cake wrapped airtight at room temperature - if it's hot where you are, this cake is best kept in an air-tight container in the fridge for up 5-7 days to prevent the frosting from melting and curdling.
Make Ahead: The cake can be baked ahead of time, cooled to room temperature then wrapped airtight and frozen up to one month. Defrost in the fridge overnight then bring to room temperature before frosting. The flour mixture for the frosting can be prepared ahead of time. Store in the fridge, and bring to room temperature before making the frosting. If making the frosting ahead, store in the fridge up to 5 days then bring to room temperature and re-whip before spreading on the cake. Tips for the Frosting:If curdling happens, your frosting is too cold. Place the bowl over steaming hot water until the vegan butter just starts to melt. Try whipping again.If your frosting is too soft and slouching, it is too warm either from over-handling or the kitchen being hot. Place the bowl in the fridge for 10-15 minutes at a time until it firms up.This frosting can be piped but will not hold up in hot temperatures as the vegan butter will melt causing the entire frosting to soften.