Measure the sparkling water and set aside. You don't want it to be too fizzy or it does weird things to the batter.

Prepare two round, square, or heart-shaped 8" (20 cm) cake pans by cutting parchment paper to fit the bottoms. Lightly spray the pans with coconut oil on the sides.

Preheat the oven to 350F/180C/gas mark 4.

Grind the sunflower seeds to a flour in the blender. Do not overblend, stop as soon as you see the flour begin to fly around.

Put the sunflower seed flour into a large bowl and use the back of a big spoon to press out any lumps. Whisk the sunflower seed flour with the tapioca flour, coconut flour, and baking soda substitute until all one color.

Separate the eggs, setting aside the yolks. Beat the egg whites with a hand or stand mixer, adding the cream of tartar gradually, until stiff peaks form. Set aside. (If using a stand mixer, remove the egg whites to another bowl. Leave the wire whisk on the machine.)

In a large bowl (or the stand mixer bowl), beat the egg yolks with the olive oil, stevia, and vanilla until lightened in color. Add the applesauce and beat until well mixed.

Add the flour mixture and coconut milk in thirds, beating well with each addition. The batter will be very stiff. Scrape down the sides of the bowl with a spatula.

With the machine off, add the sparkling water. Turn on low, gradually increasing in speed until the batter is smooth and pourable.

Fold in the egg whites by hand until evenly distributed.

Pour the batter into the two pans as evenly as possible. Rap each pan sharply on the counter 2-3 times to remove any air bubbles.

Bake for 35-38 minutes, until they are golden at the edges and just starting to crack slightly on top.

Cool on wire racks for 10 minutes, then loosen the cakes and flip them onto the wire racks. Cool completely before assembling.

To make the whipped cream: Beat cold whipping cream with two packets of organic stevia until soft peaks form. Do not overbeat or it will turn into butter.

To make whipped coconut cream: You'll need to refrigerate the coconut milk overnight. I store mine in the fridge, a tip I picked up from Liv Life Too. Use a spoon to remove as much of the firmed-up coconut milk as possible. It may not separate completely. I strain the milky water into a storage jar, adding any lumps of the coconut milkfat from the strainer into the bowl. Beat on high, gradually adding in two packets of stevia until it turns into fluffy whipped cream, about 3-5 minutes..

Place the bottom layer right side up on a cake plate or stand.

Hull most of the strawberries, saving the prettiest ones for the top layer. Mince strawberries until you have about a cup.

Spread a layer of whipped cream on top of the cake , just about to the edges. Sprinkle with minced strawberries and finely chopped mint if you like.

Add the second layer, and top as the first, but use sliced strawberries and whole mint leaves for garnish.

This cake is best the day it's made, but can be stored in the refrigerator overnight.