1. For best results, weigh the ingredients either in grams or ounces
2. Place rack at bottom third of the oven and preheat to 150 C or 300 F
3. Line the bottom and side spring of a 15 cm (6 inch) spring form cake pan with parchment. Use butter on the sides to help keep the parchment in place
4. Separate the eggs, placing whites into mixer bowl and yolks into a small bowl
5. Whip the egg whites until they start frothing, add the white vinegar, and continue whipping until soft peaks form
6. Slowly add the sweetener, 1 tbsp at a time, to egg whites, incorporating each tablespoon before adding more sweetener (allowing a few seconds between additions)
8. Add the egg yolks, using a hand whisk. Gently whisk the yolks into the whipped whites until the mixture is a uniform pale yellow
9. In a bowl, combine the coconut flour, almond flour and salt. Stir
10. Using a fine mesh strainer, add 1/3 of the flour mix and combine using a balloon whisk, before adding the second and third amounts
11. In a glass or measuring cup, combine the oil or melted butter, lemon juice and lemon rind. Stir and pour slowly into whipped egg mixture while blending gently with a spatula
12. Pour into parchment-lined (bottom and sides) 15 cm (6 inch) spring form pan. Run a knife through to remove large air pockets and then drop/tap to eliminate small air pockets
13. Bake for 35 minutes then test with a toothpick it to see if done. If not done, continue baking for 5 minute intervals until the toothpick comes out clean. Then increase the oven temperature to 170 C or 340 F for 3 minutes to make the top golden
14. Remove from oven and place on counter to cool down. When cake is at room temperature, loosen the spring and remove the rim. Gently peel off the side parchment. With the use of a wire rack or second plate, flip the cake and remove the bottom parchment liner, then again flip the cake back upright
15. Place the cake into the refrigerator for several hours until the cake is completely chilled
16. In a mixing bowl, add the mascarpone and the sweetener and whisk at low speed for 1 minute until well-combined
17. Add the whipping cream and mix at low speed for about 30 seconds, then increase the speed to high and whip until stiff peaks form. Cover the bowl with cling wrap and place in the refrigerator until ready to use
18. When the cake is completely cooled, remove from fridge and cut into half (top and bottom). Carefully remove the top layer – use support when removing the top layer so that it does not crack. Set aside
19. Place bottom half of the cake back into the spring-form pan before piping the mascarpone whipped cream frosting on top of the cut section
20. Using a piping bag and starting in the center, move in an outwardly-expanding circular motion, squeezing out a thick layer of frosting right to the edge of the cake
21. Carefully place the top half of the lemon sponge cake on top of the frosting and then repeat the piping out of frosting to the top of the cake. Repeat until there is frosting that reaches the top rim of the cake pan
22. Smooth the top surface with an offset spatula or the back of a long knife
23. Run a spatula or small knife on the inside of the pan rim, to loosen the frosting from the spring-form pan before you remove it
25. With a spatula, apply frosting to the side the cake. Smooth as well as you can
26. Refrigerate to allow the mascarpone whipped cream frosting to set before cutting and serving. Take out of fridge just before decorating and serving. Cut into 8 pieces
27. OPTIONAL: What you use to decorate the top is up to you. Fresh fruit such as thinly-sliced strawberries are both attractive and complement the lemon freshness and mascarpone whipped cream frosting. Alternatively, use lemon peel ribbons, or make swirls with some of the frosting.
When you cut the cake or want to separate the top and bottom, be very careful as this cake is more fragile than a gluten cake. Slide a thick cardboard or thin flat sheet, or very wide spatula, for support. Should the top cake portion crack in spite of your best effort, place it back on top of the middle section frosting, and as Julia Child would say in her videos, “It’s just you and me, and no one else saw it (paraphrased) so don’t worry.” After arranging the top layer just spread a very thick layer of frosting on top. When the cake has rested and you have decorated it, no one will know about the little mishap. They will be amazed at how great and lemony this grain-free and sugar-free cake tastes. As you make this a couple of times, your technique will improve and soon you will master how to make the cake because this is a very easy recipe to do.
The mascarpone frosting I used is just one type of frosting. You could substitute the Swiss Buttercream Frosting (as used in the Chocolate Swiss Roll recipe) instead.
Also, if you are serving for a more casual event such as family dinner, or coffee with friends, top the cake with confectionery sweetener. Take whatever sweetener you prefer and grind to a very fine consistency. Use a small fine sieve to dust the top.
August 29, 2021 @ 2:44 pm
This cake did not rise at all. I watched your video while doing mine and it was exactly the same. It was for my birthday. Oh well, I guess I didn’t need cake 😟
August 30, 2021 @ 7:32 am
I am so sorry to hear that the cake didn’t rise for you. I can only think of two things that may have gone wrong. One, the eggs weren’t fresh, because you need loft from the whites. Or, when combining all the ingredients, you deflated the whites. Again, I am very sorry that this didn’t turn out, and my belated birthday wishes to you!
January 21, 2022 @ 8:52 pm
I made this cake for my daughter’s birthday. I was worried when I completed making the batter. It looked more like dough than a smooth batter. Not sure where I went wrong. I’m wondering if I incorporated the flour too much into the fluffy egg mixture. …hmm. Went ahead a baked it. It’s chilling in the fridge, but I don’t know how “sponge-y” the cake will be. Maybe I should watch the video. I’ll report on the finished dessert.
January 22, 2022 @ 10:20 am
Yes, please watch the video, as technique for this cake is as important as the ingredients. It is extremely important to fold in the ingredients, a little at a time, and gently, using either a large balloon whisk or thin metal spatula, in order not to deflate the egg whites.
I hope these tips are useful. And a very Happy Birthday to your daughter!