Preheat oven to 325 F (160C). Spray a loaf pan with non-stick cooking spray with flour. You can also lightly butter (unsalted) and flour the pan.
In a medium bowl, mix together the baking powder, flour, and salt. Then whisk the sour cream and lemon juice together in a small measuring cup.
In a large bowl, combine the lemon zest and sugar. Rub it together with your fingertips until the sugar is moist and fragrant. Add the butter to the bowl and mix it till its very pale and fluffy. Mix in the eggs in 3 additions, mixing after each addition until the mixture is smooth. Start adding in the dry ingredients in 3 additions and the sour cream mixture in 2 additions, starting and ending with the dry ingredients.
Transfer the batter to the prepared pan. After topping off the pan tap the pan on your work surface to release air bubbles. Bake the cake for about 60 minutes.
Transfer the pan to a wire rack and let the cake cool for 10 minutes, then turn it out.
Making the syrup:
Combine the sugar and lemon juice in a small saucepan and heat it up while stirring frequently, until the sugar dissolves. Bring the mixture to a simmer, then remove from the heat and set aside.
Once you’ve turned the cake out of the pan, brush the top and sides with the lemon syrup. use all of the syrup. Let the cake cool completely.
Combine the confectioners’ sugar and lemon juice in a small bowl and stir until smooth. Pour over the top of the cake, covering completely. Let the glaze set for at least 15 minutes.