In a large bowl, whisk together the gluten-free flour, baking powder, baking soda, and salt.
In a separate bowl, mix together the date sugar, milk, vinegar, oil, lemon juice, lemon zest, and vanilla extract. Gradually add the wet ingredients into the dry ingredients.
Fold cake batter just until combined then gently fold in blueberries.
Pour the batter into an oiled loaf pan and smooth the top. Bake at 350℉ for 50-60 minutes, or until a toothpick inserted into the center comes out clean. Let cake completely cool.
In a small bowl, whisk together powdered sugar, lemon juice, and lemon zest. Drizzle glaze over cooled cake loaf and serve.