Preheat oven to 350 degrees. Spray a 9 by 5 inch loaf pan with gluten free non-stick cooking spray and line with a piece of parchment paper that overhangs on the sides.
Whisk together the brown rice flour, tapioca starch, salt and baking powder. Beat the Poppy Seed filling, eggs, oil and lemon jest on medium high speed of a mixer until it doubles in volume, 2 – 3 minutes. Turn the mixer to low and add the flour mixture slowly. Add the milk and mix until combined. Scrape the sides and bottom of the mixing bowl well with a spatula. Pour the batter into the prepared pan and bake 50 – 60 minutes or until browned and a tooth pick inserted into the loaf comes out clean. Let cool in the pan for 5 minutes then remove to a wire rack to finish cooling.
Mix the lemon juice with the powdered sugar until smooth. Drizzle onto the cooled loaf and let set for a few minutes.