Prepare the pretzel crust: Preheat your oven to 350°F (175°C). In a medium bowl, combine the crushed pretzels, melted butter, and 3 tablespoons of sugar until well mixed. Press this mixture firmly into the bottom of a 9×13 inch baking dish to form an even layer. Bake for 10 minutes, then remove and cool completely.
Mix the cream cheese layer: In a large bowl, beat the softened cream cheese and 1 cup sugar together until smooth and fluffy, about 3-4 minutes. Gently fold in the whipped topping until completely incorporated. Be careful not to overmix or you’ll lose the fluffiness.
Seal the crust completely: Spread the cream cheese mixture evenly over the cooled pretzel crust, making sure to seal it all the way to the edges. This creates a barrier that prevents the gelatin from seeping through to the crust and making it soggy.
Chill the base layers: Refrigerate the pretzel and cream cheese layers for at least 30 minutes to set firm before adding the strawberry topping.
Prepare the strawberry layer: Dissolve the strawberry gelatin in 2 cups of boiling water, stirring for about 2 minutes until completely dissolved. Add the sliced strawberries (and optional lemon juice if using). Let the mixture cool to room temperature but don’t let it set completely – it should be slightly thickened but still pourable.
Complete the dessert: Carefully pour the cooled strawberry mixture over the cream cheese layer. Return the dish to the refrigerator and chill for at least 2-3 hours, or preferably overnight, until the gelatin is completely set.
Serve and enjoy: Cut into squares and serve chilled. For the cleanest cuts, dip your knife in hot water and wipe it clean between slices.