Preheat fanforced oven to 160 degrees c (180 degrees for non fan forced)
The Cake: In a large mixing bowl, add the softened butter and granulated sweetener. Use electric beaters to beat on high until creamy and fluffy.
Add the eggs, 1 at a time, beating each one in with the electric beaters.
Add in the flour, cream of tartar and bicarb, followed by the milk. Use a large spoon to fold in, turning the bowl and you gently stir through. (do not beat or mix roughly as this will make the cake tough)
The Cooking: Spoon cake mixture into a lined loaf tin, running the back of a spoon over the top to smooth out the mixture. (I use a silicone loaf tin, lined with baking paper).
Bake in the oven for 40 minutes.
Once cake is cooked, remove from oven and set aside on a cooling rack.
The Syrup: Combine ½ cup lemon juice and 2 tablespoons granulated sweetener in a saucepan and heat on medium for 2 minutes or until all the sweetener has dissolved. Increase the heat to high and bring to the boil for 4 to 5 minutes or until thickened slightly, then remove from heat.
Using the cake skewer, poke about a dozen holes through the top of the cake, and drizzle the lemon sauce gently over the warm cake.
Let the cake sit to cool to room temperature, then remove it from the cake tin.