Step 1: Preheat oven to 350°F (175°C). In a medium bowl, combine crushed pretzels, melted butter, and granulated sugar. Press mixture evenly into the bottom of a 9x13 inch baking dish. Bake for 10 minutes. Remove from oven and let cool completely.
Step 2: In a large bowl, beat the softened cream cheese and powdered sugar until smooth and creamy. Fold in the thawed whipped topping until no streaks remain. Spread this mixture evenly over the cooled pretzel crust, making sure to spread it all the way to the edges to create a seal.
Step 3: In a separate bowl, dissolve the gelatin in boiling water. Stir until completely dissolved. Add the whole berry cranberry sauce and stir until well combined. Let this mixture cool to room temperature, stirring occasionally, until it begins to thicken slightly (about 20-30 minutes).
Step 4: Carefully pour the cooled cranberry-gelatin mixture over the cream cheese layer. Refrigerate for at least 4 hours, or until completely set. Cut into squares and serve chilled.