Preheat your oven to 180°C. Grease an 8 x 8-inch baking dish and line with parchment paper.
For the biscuit base, mix the ingredients together in a large bowl until combined. Press into the tin and bake until golden (about 20 minutes).
For the topping, whisk the egg whites with the cream of tartar in a freestanding mixer until soft peaks form. Gradually add the sugar while the mixer is still on, add the flour and whisk this at a low speed. Then, fold through the lemon curd.
Reduce the oven temperature to 140°C. Pour your mixture over the biscuit base and place it back in the oven for another 30-35 minutes, it should be nicely golden and risen.
Allow to cool completely, dust with icing sugar, and slice into 10 bars.