Preheat the oven to 160°C and lightly grease and line a 15 cm cake tin. For a taller cake, use a smaller, deeper tin.
Separate the egg yolks and egg whites into two bowls.
Whisk the egg yolks with the ricotta, monk fruit sweetener, vanilla, lemon zest and baking powder until smooth.
Whip the egg whites until stiff peaks form.
Gently fold the egg whites into the yolk mixture, being careful not to deflate the mixture.
Pour into the prepared tin and bake for 20 minutes at 160°C, or until puffed and lightly golden. A toothpick inserted into the centre should come out mostly clean, with a few moist crumbs.
Allow to cool completely before serving. The cake will naturally settle as it cools.
Blend the strawberries, monk fruit sweetener and lemon juice until smooth. Transfer to a small saucepan and simmer over low-medium heat, stirring occasionally, until slightly reduced and thickened. Remove from the heat and allow to cool — it will thicken a little more as it cools.