Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
In a large bowl, cream together the sugar and butter until light and fluffy.
Beat in the eggs one at a time, then mix in the 1/2 cup lemonade concentrate.
In a separate bowl, whisk together the flour, baking powder, and salt.
Gradually add the dry ingredients to the wet mixture, alternating with milk. Mix until just combined.
Pour the batter into the prepared dish and spread evenly.
Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
Let the cake cool slightly.
In a small bowl, whisk together powdered sugar and 2 tablespoons lemonade concentrate until smooth.
Pour the glaze over the warm cake and let it soak in. Cool completely before serving.