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

In a large bowl, combine granulated sugar and lemon zest. Use your fingers to rub the zest into the sugar until fragrant and pale yellow.

Whisk the room-temperature eggs, oil, sour cream, 3 tablespoons lemon juice, and vanilla extract into the lemon sugar until smooth and completely combined.

In a separate bowl, whisk together the flour, poppy seeds, baking powder, baking soda, and salt.

Add the dry ingredients to the wet ingredients. Fold gently with a spatula just until combined and no dry streaks remain. Do not 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. Tent with foil after 40 minutes if browning too quickly.

Let the bread cool in the pan for 15 minutes, then transfer to a wire rack to cool completely to room temperature.

Once the loaf is completely cool, whisk together the powdered sugar and 2-3 tablespoons of fresh lemon juice until a thick glaze forms. Drizzle over the bread, let set, slice, and serve.