Preheat your oven to 350°F (175°C). Grease and flour your loaf pan to prevent sticking.
In a large mixing bowl, whisk together the cake flour, all-purpose flour, baking powder, baking soda, and salt until well combined.
In another bowl, beat the eggs and sugar together until light and fluffy. Add the lemon zest, lemon juice, melted butter, sour cream, and vanilla extract. Mix until everything is well combined.
Gradually add the dry ingredients to the wet mixture, folding gently with a spatula until just combined. Be careful not to overmix.
Pour the batter into the prepared loaf pan and spread it evenly. Bake for about 60-70 minutes, or until a toothpick comes out clean.
While the cake is baking, prepare the lemon syrup by combining lemon juice and sugar in a small saucepan. Heat until the sugar dissolves. Set aside to cool.
Once the cake is done, let it cool in the pan for 10 minutes before transferring it to a cooling rack. Brush the lemon syrup over the top while still warm.
In a bowl, whisk the sifted powdered sugar with lemon juice to create a smooth glaze. Adjust consistency as needed.
Once cooled, drizzle the lemon glaze over the cake and let it set before slicing.