Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Combine pretzels, pecans, cranberries, brown sugar, and 1/2 cup melted butter together in a bowl.
Beat sweet potatoes together in a bowl until smooth; add evaporated milk, sugar, vanilla extract, and remaining 1/2 cup melted butter and mix until smooth. Spoon mixture into the prepared baking dish; sprinkle pretzel mixture over the top.
Bake in the preheated oven until edges are bubbling, 25 to 30 minutes.
