Preheat the oven to 175˚C (155 fan). Spray an 8-inch/20cm round cake pan with baking spray, rub inside surface of pan with a paper towel to cover evenly with the spray. Line bottom of pan with parchment paper and spray parchment paper lightly. Set aside.
In a large bowl, combine the yogurt and eggs, stirring until well blended.
Add the HGG paleo baking mix, baking powder and zest, mixing to just combine.
Add the oil and stir well. Don’t worry, at first it will seem to separate, but keep stirring till smooth.
Pour the batter into prepared pan.
Bake for 30 minutes, until the cake feels springy to the touch and a toothpick or cake tester inserted into the center comes out clean. Be careful not to over bake.
Cool cake on a wire rack for 10 minutes; then turn it out of the pan onto the rack.
Combine the lemon juice and powdered sugar in a small bowl and stir until smooth. With a pastry brush, gently pat the glaze all over the cake. Just keep going over the cake till the glaze is gone. Some of it will drip off, but most of it will soak in. Allow cake to cool completely.