Preheat your oven to 350°F (175°C). This ensures that the bars cook evenly.
Line your 9x9 inch baking pan with parchment paper or lightly grease it. This will make it easier to lift the bars out once they’ve cooled.
In a large mixing bowl, combine the melted unsalted butter, large egg, sweetened condensed milk, lemon juice, vanilla extract, and lemon extract (if using). Whisk until the mixture is smooth and well combined.
In a separate bowl, mix together the all-purpose flour, lemon zest, and salt. Gradually add this dry mixture to the wet ingredients, stirring with a spatula until just combined. Be careful not to overmix!
Gently fold in the chopped maraschino cherries, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared baking pan, spreading it out evenly. Bake in the preheated oven for about 25-30 minutes, or until the edges are lightly golden and a toothpick inserted in the center comes out clean.
Once baked, remove the bars from the oven and allow them to cool in the pan for about 10 minutes. Then, lift them out using the parchment paper (if used) and let them cool completely on a wire rack. If desired, drizzle with melted white chocolate before slicing into squares.
