Preheat oven to 350°F and spray a 9x5 inch loaf pan with non-stick spray.

In a large bowl, sift and whisk together the flour, xanthan gum, baking powder, baking soda and salt. Whisk in the poppyseeds, sugar and lemon zest.

In a medium bowl, whisk together the milk, eggs, vegetable oil, lemon juice and vanilla. Pour the wet ingredients into the dry ingredients and stir until completely combined.

Transfer the batter to the prepared baking pan and bake for 55 minutes to 1 hour or until a toothpick comes out clean.

When the bread is done, cool in the pan for 10 minutes than remove it from the pan and cool completely on a wire rack.

To make the glaze, stir together the powdered sugar, lemon juice and vanilla extract. If the glaze is too thick, stir in some water ¼ tsp at a time until it reaches your desired thickness. Pour the glaze over the top of the completely cooled bread and let it set, about 5-10 minutes before serving.