Make the lemon pound cake

• Preheat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with parchment, leaving a little overhang on the long sides so the cake lifts out cleanly later.
  
• In a medium bowl, whisk together 2 cups (240g) all-purpose flour, 1 teaspoon (4g) baking powder, and 1/2 teaspoon (3g) kosher salt. In a small bowl, rub 2 tablespoons lemon zest into 1 1/2 cups (300g) granulated sugar with your fingertips until the sugar feels damp and smells intensely lemony.
  
• In a large bowl, beat 1 cup (227g) softened unsalted butter with the lemon sugar on medium speed for 3 to 4 minutes, until the mixture looks pale, fluffy, and lighter in texture. Add 4 large eggs one at a time, beating well after each addition. If the batter looks slightly curdled, that is fine.
  
• Mix in 1/2 cup (120g) sour cream, 2 tablespoons (30ml) fresh lemon juice, and 1 teaspoon (5ml) vanilla, if using. Add the dry ingredients and mix on low just until no flour streaks remain. Scrape the batter into the prepared pan and smooth the top.
  
• Bake for 50 to 60 minutes, until the top is deeply golden, the center springs back lightly, and a tester inserted into the middle comes out with a few moist crumbs but no wet batter. If the top is browning too fast near the end, tent it loosely with foil.
  
• Cool the cake in the pan for 15 minutes, then use the parchment to lift it onto a rack. Let it cool completely before glazing. This part matters. A warm cake will drink the glaze instead of wearing it.
  
• For the glaze, whisk 1 cup (120g) powdered sugar with 2 tablespoons (30ml) fresh lemon juice. Add up to 1 tablespoon (15ml) more juice, a little at a time, until it flows slowly off the whisk in a thick ribbon. Spoon it over the cooled cake and let it set for 15 to 20 minutes.
  
• Slice with a sharp serrated knife and serve once the glaze has turned glossy and lightly firm. You should see a fine, buttery crumb and smell lemon before the slice even reaches the plate.