Simple, caramelized brown sugar pie with a rich, custard-like filling is a humble, family heritage dessert. This old-fashioned, Southern classic transforms pantry staples into something extraordinary.
Preheat oven to 350°F (175°C) with the rack in the center position for even baking.
Melt the unsalted butter in a medium saucepan over low heat; once melted, remove from heat and let it cool slightly to avoid scrambling the eggs.
In a large bowl, combine melted butter, light brown sugar, and flour; whisk until smooth and there are no lumps for a silky custard texture.
Add eggs one at a time, followed by evaporated milk, vanilla extract, and salt; whisk gently until fully incorporated but do not over-mix to prevent air bubbles.
Pour filling into the unbaked deep dish pie crust. Set pie on a baking sheet to catch any overflow. Bake at 350°F for 45-55 minutes, rotating halfway, until the filling is set but still slightly wobbly in the center.
Cool pie completely on a wire rack to allow custard to firm up, at least 2 hours, before slicing and serving for the best texture.