Spray a 6 inch round cake pan (that fits in the Instant Pot) with nonstick coconut oil spray. Set aside.
Place 2 paper towels into a colander and place the grated carrot and grated zucchini
onto the paper towels and press down on grated vegetables with your hands in the colander to drain the excess liquid.
In a large bowl with an electric hand mixer or stand mixer add almond flour, erythritol sweetener, baking powder, baking soda, cinnamon, cardamom, nutmeg, eggs, heavy cream, butter, vanilla extract, grated carrot and grated zucchini. Beat on medium until thoroughly blended.
Pour cake batter into the prepared pan. Cover the top of the pan tightly with a sheet of aluminum foil.
Add 1 ⅔ cup water to the Instant Pot and place the steamer rack into the pot. Place covered cake pan on the steamer rack.
Close, lock lid, and flip the steam release handle to the Sealing position. Select Pressure Cook (Manual) on High Pressure or Cake Setting (if your Instant Pot has the Cake button) and set the cook time for 44 minutes.
Once cook time is complete, let the pressure naturally release for 10 minutes and then Quick release the remaining pressure.
Open the lid and carefully grasp the rack handles to lift the cake pan out of the pot. Remove the aluminum foil cover and let the cake cool for 25 to 30 minutes.
While the cake is cooling, you can make the frosting.
In a large bowl add cream cheese, 3 tbsp erythritol sweetener, lemon juice, vanilla extract, and heavy cream. Use an electric hand mixer and beat on high until combined and creamy.
Once the cake has cooled completely, frost the cake, sprinkle with walnuts, slice and serve. Store covered in the fridge for up to 5 days.
*all nutritional data are estimates based on the products I used*Yield: 6 slices, Serving size 1 slice, Amounts per serving- Net Carbs: 4.5g per serving