Preheat an oven to 450 degrees F (230 degrees C). Pour melted butter into a 2-quart baking dish.
Whisk pumpkin, 1 cup sugar, evaporated milk, flour, eggs, vanilla extract, salt, and baking soda in a large bowl; pour into the prepared baking dish. Combine remaining 1/2 cup sugar and cinnamon in a small bowl; sprinkle over pumpkin mixture.
Bake in the preheated oven until center is set, about 30 minutes.