Preheat your oven to 325°F (163°C). This ensures that your cake bakes evenly.
Grease your 9x5 inch loaf pan with butter or non-stick spray, then set it aside.
In a large mixing bowl, cream together the softened butter and granulated sugar using an electric mixer. Beat until the mixture is light and fluffy, about 3-5 minutes.
Add the eggs, one at a time, mixing well after each addition. This helps to incorporate air into the batter.
In a separate bowl, sift together the all-purpose flour and lemon extract. Gradually add this mixture to the butter-sugar-egg mixture, alternating with the lemon-lime soda, starting and ending with the flour mixture. Mix until just combined.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula.
Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes. Then, transfer it to a cooling rack to cool completely.
In a small bowl, whisk together the sifted confectioners' sugar, melted butter, vanilla extract, and lemon juice until smooth. Drizzle over the cooled cake.