1.   Preheat oven to 330 F or 166 C. Line 8×8-inch or 20 X 20 cm square cake pan with parchment paper. Set aside

2.   Use 2 bowls to separate the egg whites and yolks. Add 1 tsp of lemon juice to the egg white bowl. Using either your stand mixer or hand mixer, whip the egg whites to a stiff peaks stage. Set aside

3.   To the bowl with the egg yolk, add the granulated sweetener, whip until the eggs are at a pale-yellow color. Pour in the melted butter and vanilla, whip to combine. Sprinkle in the almond flour, lupin flour and glucomannan, mix until fully incorporated. Add lemon zest and lemon juice, mixing to combine. Slowly pour in the cream, and water, mixing on low speed until well combined.

4.   Gently add the beaten egg whites into the mixture and whisk by hand. Don’t worry if there are small lumps of egg whites left in the mixture. These lumps will create the top layer of the cake during baking.

5.   Pour the batter (batter will be very thin and lumpy) into the prepared cake pan

6.   Place in the middle position of the preheated oven. Bake for 30 minutes for a more runny custard bottom or 40 minutes for a more firm custard base (as I did) or until the center is barely jiggly and the top is firm to the touch. Start checking the cake after 30 minutes as baking time may vary depending on your oven or pan. Do not over bake the cake, for a custard layer. Bake a few more minutes for a more solid cake.

7.   Once the cake is done, let the cake cool to room temperature in the pan. Dust with a sweetener ground to a fine confectionery powder. Scoop if custard is present, or cut into 9 squares, then serve. Store leftovers in an airtight container in the refrigerator for several days. Enjoy!