Cook the Lemon: Place the whole lemon in a deep saucepan and cover completely with cold water. Use a small heatproof dish to keep it submerged. Bring to a gentle simmer over medium heat and cook for 20 minutes, until the lemon is very soft. Drain and let cool completely.
1 whole lemon
Once cool, cut the lemon into chunks, no need to remove any visible seeds. Blend the lemon with the olive oil until fully smooth and emulsified. Set aside.
1 c extra virgin olive oil
Prep the Oven and Pan: Preheat the oven to 335°F (170°C). Line the base and sides of a 9-inch (23 cm) springform pan with parchment paper.
Mix the Dry Ingredients: In a bowl, whisk together the almond flour, gluten free 1:1 flour or all-purpose flour, baking powder, baking soda, salt, and lemon zest. Set aside.
3 c almond flour, ½ c Gluten Free 1:1 flour, ½ teaspoon baking powder, ½ teaspoon baking soda, ¼ teaspoon salt, Zest of three lemons
Build the Batter: In a large bowl, whisk the eggs and caster sugar until pale and fully combined. Whisk in the lemon and olive oil mixture until smooth. Add the dry ingredients and gently fold until no dry pockets remain. The batter will be thick but pourable.
4 eggs, 1 ¼ c caster sugar
Bake the Cake: Spread the batter evenly into the prepared pan. Bake for 60 to 65 minutes, until the top feels set, lightly golden, and a toothpick inserted in the center comes out clean or with a few moist crumbs.
Cool the cake in the pan for 1 hour, then carefully invert onto a wire rack and let cool completely.
Make the Lemon Syrup: In a small saucepan, combine the sugar and lemon juice. Heat over medium-low, stirring until the sugar dissolves. Bring to a simmer and cook for 6 to 8 minutes, stirring frequently, until slightly thickened and glossy. Cool to room temperature.
5 tbs castor sugar, ¾ c lemon juice
Make the Cream Topping: In a stand mixer fitted with a whisk attachment, beat the mascarpone and sugar on medium speed until smooth. Increase to medium-high and slowly drizzle in the heavy cream. Stop as soon as stiff peaks form and the mixture is smooth and billowy.
1 c mascarpone cheese, 1 c sugar, 1 ¾ c heavy cream
Finish and Serve: Spread the whipped mascarpone cream over the cooled cake. Drizzle generously with lemon syrup just before serving.