Pour the boiling water into a medium bowl and add the black cherry gelatin mix, stirring constantly for about 2 minutes until completely dissolved with no granules remaining. Stir in the undrained crushed pineapple and the blueberry pie filling, mixing until evenly combined. Pour this mixture into a 9x13 inch baking dish or similar size and refrigerate for about 2 hours until the gelatin is set but still slightly jiggly to the touch—this gives the topping layer something to adhere to rather than sinking through.

While the gelatin base is chilling, combine the softened cream cheese and granulated sugar in a medium bowl, beating together with an electric mixer or vigorously by hand until smooth and well blended. I find that room-temperature cream cheese mixes much more smoothly than cold cream cheese, so if yours is stiff, let it sit out for 10-15 minutes first. Gently fold in the thawed whipped topping using a spatula, being careful not to deflate the whipped topping—use a folding motion rather than stirring to maintain the airy texture.

Once the gelatin base is set, spread the creamy topping mixture from Step 2 evenly over the top, using an offset spatula or the back of a spoon to create an even layer. Sprinkle the finely chopped pecans and fresh blueberries across the top for both flavor and visual appeal. I like to add the pecans and blueberries just before serving for maximum freshness, but you can do this step up to 1 hour ahead. Refrigerate for at least 30 minutes before serving to allow the flavors to meld and the topping to set slightly.