Preheat oven to 350 degrees F.
Make the Cake: Combine mashed sweet potato, grated carrot, eggs, honey, and vanilla in your food processor or high-powered blender. Blend until mixture is smooth.
Add in remaining ingredients. Blend, stopping ever so often to scrape the sides, until the batter has a smooth, thick texture.
Scoop batter into a parchment-lined 8″ x 8″ glass baking pan. Use a spatula to spread the batter to the sides of the pan, creating an even, level layer.
Place the pan in the oven and bake at 350 degrees for 40 minutes.
Remove the cake from the oven and cool in the pan for 10 minutes. Then, transfer to a cooling rack to cool to room temperature.
Make the Frosting: In a small bowl, whisk together shortening, maple syrup, and vanilla. Whisk in tapioca flour, 1 tablespoon at a time. Whisk until smooth.
Spread the frosting over the cooled cake.
Cut and serve.
Best stored in fridge up to one week.