Preheat the oven to 170 C / 340 F (conventional).
In a small pan, sauté the onion in olive oil with ¼ teaspoon of salt for about 5-6 minutes, until soft and golden.
In the meantime, prepare the rest of the ingredients. When you grate the carrots and sweet potatoes, I suggest to press them firmly against the side of the bowl to squeeze some of the juice out. Discard half of the juice. You don’t have to squeeze all of the juice out as some of it will go to moisten the cake, but you don’t want too much excess liquid.
In a large mixing bow, combine the grated carrots and sweet potatoes with the rest of the cake ingredients and the pre-cooked onions. Use clean hands to mix and work through the mixture until everything is well incorporated.
Grease a round spring form cake tin with coconut oil and dust evenly with tapioca or cassava flour. This will give our cake a little crust and stop it from sticking to the tin.
Transfer the meat and carrot mixture to the cake tin and spread evenly on the top.
Place in the oven, middle shelf, and cook for 1 hour.
Remove from the oven and allow to cool down slightly while still inside the tin.
Then release the spring and remove the cake from the tin onto a plate. You can turn it upside down onto another plate to the remove the tin’s bottom.
Allow the cake to cool to just warm or room temperature.
Time to decorate! Spread the mayonnaise over the top and decorate with carrots, parsley, seeds, lemon and orange zest and some black pepper.