Preheat oven to 350°F (175°C), grease and line a 9x5-inch loaf pan with parchment paper. Whisk together the 2 cups flour, 2 tsp baking powder, and 1/2 tsp salt in a large bowl.

In a separate bowl, whisk the 1 cup granulated sugar and 3 large eggs for 1 minute until slightly pale, then add the 1/2 cup sour cream, 1/2 cup vegetable oil, 2 tbsp lemon zest, 3 tbsp fresh lemon juice, and 1 tsp vanilla extract and whisk until smooth.

Pour the wet ingredients into the dry ingredients and fold with a spatula until just combined with no dry streaks. Stop as soon as the flour disappears.

Pour the batter into the prepared pan, spread level, and bake at 350°F (175°C) for 50 to 55 minutes until a toothpick comes out clean. Cool in the pan for 15 minutes, then lift onto a wire rack and cool fully, about 1 hour.

Whisk the 1 1/2 cups sifted powdered sugar and 3 tbsp fresh lemon juice into a smooth, thick glaze. Pour over the cooled loaf, let it set for 20 minutes until opaque, then slice and serve.