In a bowl, add the ground oats, cornstarch, baking powder and salt. Set aside.
Separate eggs in two different bowl.
Add the sweetener and lemon juice to the egg whites and beat with a mixer for 3-4 minutes, until stiff peaks from.
Add the sweetener and vanilla extract to the egg yolks and beat until pale and foamy.
Sift the dry ingredients into the egg yolk mixture and stir until combined. Then add the milk and mix it in.
Pour the egg whites into the egg yolk mixture and gently fold in with the spatula.
Pour the cake batter into the greased baking dish and bake for 30 minutes at 340F (170C).
Let it cool completely, then poke the holes using a fork.
Combine the milks, heavy cream and maple syrup and pour over the cake.
Let it soak and chill in the fridge overnight.
Frost with a whipped cream and serve with fresh strawberries or dust with cinnamon and cocoa powder.