Preheat your oven to 350°F (175°C).
Grease a 9x5-inch loaf pan with unsalted butter and dust with gluten-free flour or line with parchment paper.
In a medium bowl, whisk together the gluten-free flour, baking powder, baking soda, and salt.
In a large mixing bowl, cream the softened butter and granulated sugar together using an electric mixer on medium speed for about 3-5 minutes until light and fluffy.
Add the eggs one at a time, mixing well after each addition. Then mix in the lemon zest, lemon juice, and vanilla extract until well combined.
Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk, starting and ending with the dry ingredients. Mix until just combined.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake in the preheated oven for 50-60 minutes, checking for doneness with a toothpick.
Allow the cake to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.