1. Preheat the oven at 3500F (177°C). Grease at 9x5 inch loaf pan.
2. To make the cake: Whisk the Maida Replacer Flour, Baking Powder and salt to together in a large bowl. Set aside.
3. Beat the butter on high speed with a whisker in a large bowl until smooth and creamy, about 1 minute. Add the granulated sugar and beat on high speed for 2 minutes until creamed.
4. With the mixer running on low speed, add the eggs on at a time. Once the eggs is completely mixed in, stop the mixer. Add the sour cream, lemon juice, lemon zest and vanilla extract, then beat on medium speed until combined. The mixture may look curdled as a result of the varying textured combining. This is normal and the batter will come together when you at the dry ingredients in the next step.
5. With the mixture running on low speed, slowly add the dry ingredients just until combined. If needed, run a whisk throw the batter few time to ride any large lumps. Avoid over mixing. Batter is thick.
6. Spread the batter into prepared loaf pan and bake for 45-60 minutes, tenting the cake with aluminum foil halfway through baking to prevent the top from over browning. Pound cakes are dense and take a while to bake in the oven. Baking times vary, so keep an eye on yours and don't be alarmed if yours is taking longer. The cake is done when a toothpick inserted in the canter comes out mostly clean. A couple moist crumps are OK.
7. Remove the cake from the oven and place on a wire rack. Allow cake to cool in the pan on the wire rack for 1 hour, then carefully remove the slightly warm cake from the pan. You can add the icing while the cake is still warm or weight for it to cool.
8. Make the icing: Whisk all the icing ingredients together and pour over cake. Serve immediately or wait until the cake cools completely, which promises neater slices.
9. Cover and store left over cake for up to 3 days at room temperature or up to 1 week in the refrigerator.