Preheat oven to 325˚F (163˚C). Line a large baking sheet with parchment.
In a large bowl, beat together the butter and sugar until light and fluffy.
Beat in the egg, scraping down the sides of the bowl as needed to evenly mix, followed by the orange zest and almond extract.
Mix in the flour, baking powder, cardamom, and salt until just combined and a smooth dough forms.
Divide the dough into 2 equal portions.
Roll each piece into a rope about 14 inches (35.5 centimeters) long.
Place the ropes lengthwise on the parchment-lined baking sheet at least 5 inches (12.7 centimeters) apart and lightly flatten until they are each about 2 1/2 inches (6 centimeters) wide.
Brush the tops with milk and sprinkle heavily with the sliced almonds.
Bake in preheated oven until the cookies spread and are lightly browned around the edges, 20-22 minutes.
Remove the baking sheet from the oven and allow to cool for 5 minutes.
After 5 minutes, while still warm, use a sharp knife to cut one of the sheets into individual cookie bars slightly on the diagonal about 1 inch (2.5 centimeters) wide. Repeat with the other sheet and transfer the bars to a wire rack to cool to room temperature.
In a small bowl, combine powdered sugar and almond extract. Whisk in the orange juice until smooth and thin enough to drizzle.
Drizzle the glaze on cooled cookie bars.
Allow to set briefly before serving.