Preheat your oven to 350°F (175°C). Grease and line a 9x5-inch loaf pan with parchment paper for easy removal.

In a small bowl, combine the granulated sugar and lemon zest. Use your fingers to rub the zest into the sugar until fragrant. This step enhances the lemon flavor. Set aside.

In a separate bowl, whisk together the flour, baking powder, and salt. Set aside.

In a large mixing bowl, cream the softened butter with the lemon sugar mixture until light and fluffy.

Mix in the eggs, vanilla extract, lemon juice, sourdough discard, and Greek yogurt. Stir until the mixture is smooth and fully combined.

Add the dry ingredients to the wet ingredients. Using a rubber spatula, gently fold the batter together until just combined. Be careful not to overmix.

Pour the batter into the prepared loaf pan and smooth the top.

Bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. If wet batter remains, continue baking and check again every few minutes.

Allow the cake to cool in the pan for about 10–15 minutes, then transfer to a wire rack to cool completely before glazing.

In a small bowl, whisk together powdered sugar, lemon juice, lemon zest, and vanilla extract until smooth.

Once the cake is completely cool, drizzle the glaze evenly over the top. Slice and enjoy!