Preheat oven to 350°F. Grease a loaf pan and put parchment paper on the bottom of the pan.
Whisk flours, baking powder, baking soda and salt together in a medium bowl.
Combine sugar, eggs, lemon zest and lemon juice in a large bowl. Stir in the butter. Add sour cream and vanilla. Mix well to combine.
Sprinkle half the flour mixture into the wet ingredients. Fold gently until just combined. Fold in the rest of the flour mixture until just combined.
Pour the batter into the prepared pan. Bake for 20 minutes and then reduce heat to 325°F and bake for another 30-35 minutes or until a toothpick comes out clean. Allow the loaf to cool in it's pan for 15 minutes before removing it from the pan.
For the lemon syrup, heat lemon juice and sugar in a small saucepan until the sugar dissolves. Once dissolved, cook for another 3 minutes.
Use a toothpick and poke holes all over the top of the loaf. Brush the lemon syrup over the loaf.
For the lemon glaze, whisk icing sugar and 2 tablespoons of lemon juice together. Add more lemon juice if needed until you get the right consistency. You want the glaze to be just a bit runny, but not too much that it will all fall down the sides of the loaf.
Store the lemon loaf in an airtight container at room temperature for up to 5 days.
Don't have cake flour? Make your own: Measure out 1 ½ cups of all purpose flour. Remove 1.5 tablespoons of flour and add 1.5 tablespoons of cornstarch to the flour. Sift the flour and cornstarch together twice to aerate the mixture to make it similar in consistency to cake flour.
Take out the eggs and sour cream 30-60 minutes before starting this recipe.
Lemon zest is the bright yellow layer of the lemon peel. Use a micro plane or box grater to grate. Make sure you don't get the white pith layer. It is very bitter.
Store the lemon loaf at room temperature in an air tight container. Do not store it in the fridge as it would dry out the loaf.
You can freeze the loaf after it has been baked and before you add the syrup and glaze. Freeze for up to 3 months. Allow the loaf to thaw at room temperature and then add the syrup and glaze.