Preheat your oven to 350°F. Add the chopped strawberries, sugar, and lemon juice to a medium saucepan.

Cook over medium-low heat, stirring occasionally, until the mixture begins to bubble. In a small bowl, whisk together the cornstarch and water, then pour it into the strawberries while stirring.

Continue simmering over medium-low heat for 6–8 minutes, stirring every minute or so, until the filling has thickened. Remove from the heat and set aside.

In a large bowl, whisk together the butter, granulated sugar, and brown sugar until light and creamy. Mix in the vanilla extract, lemon extract, and lemon juice. Add the flour and mix until a soft dough forms.

Grease an 8x8-inch baking pan with butter and line it with parchment paper. Press about ¾ of the dough evenly into the bottom of the pan. Spread the strawberry filling over the dough, then crumble the remaining dough on top. Bake for 42–44 minutes, or until lightly golden.

Allow the bars to cool completely before slicing. Dust with powdered sugar if desired. Store covered at room temperature for up to 8 days or in the refrigerator for up to 10 days.