Preheat the oven to 350°F (175°C). Line a 9x5-inch loaf pan with parchment paper or grease with oil.

In a small bowl, whisk together the gluten-free flour, baking powder, and salt. Set aside.

Add the granulated sugar and lemon zest to a large bowl. Rub the lemon zest into sugar until yellow and fragrant, about 1-2 minutes.

Add the vegetable oil, eggs, sour cream, vanilla extract and lemon juice to the sugar mixture. Mix for 2-3 minutes, until combined and smooth.

Add the dry ingredients to the wet ingredients, mixing until no more streaks of flour remain.

Pour the batter into a 9x5-inch loaf pan lined with parchment paper.

Bake at 350°F (175°C) for 45-55 minutes, until the top of the lemon cake is lightly browned and a toothpick or skewer inserted into the center comes out with moist crumbs. Do not open the oven until the cake is almost done cooking, otherwise the center may collapse.

Cool the cake in the pan for 20-30 minutes before turning it out onto a wire rack to finish cooling.

In a small bowl, combine the powdered sugar and lemon juice. Whisk until smooth and well combined. The drizzle should not be too thin, so that it doesn't fall down the sides of the cake.

You can drizzle the cake when warm or fully cooled. If drizzled when warm, the glaze will melt into the cake a bit. If drizzled when cool, the glaze will form a thick white drizzle, similar to the photos in this post.

Immediately after glazing the cake, sprinkle with additional lemon zest.

Let the glaze set completely before slicing the cake to serve.

Slice the cake in 10 equal pieces.