Step 1

Preheat oven to 350 degrees F (175 degrees C). Grease an 8-inch square baking dish.

Step 2

Beat flour, white sugar, butter, and sea salt together in a bowl using an electric mixer until well mixed. Whisk eggs, 2 tablespoons lemon juice, and 1 tablespoon lemon zest together in a separate bowl; mix into flour mixture and beat on medium speed until smooth, about 3 minutes. Pour batter into the prepared baking dish.

Step 3

Bake in the preheated oven until a toothpick inserted in the center comes out clean, 23 to 25 minutes. Cool until bottom of dish is warm to the touch.

Step 4

Whisk confectioners' sugar, 1/4 cup lemon juice, vanilla extract, and lemon zest (to taste) together in a bowl until smooth; spread over brownies.