Chill your tools: Pop a mixing bowl and whisk/beaters in the fridge for 10 minutes. Cold tools whip cream faster.

Whip the cream: Beat heavy cream to soft peaks. Add a pinch of salt and vanilla, then whip to medium peaks. Set aside. (If using whipped topping, skip this step.)

Make the lemon cream: In a separate bowl, whisk instant lemon pudding mix with sweetened condensed milk and lemon juice until smooth and thick. Fold in lemon zest.

Combine gently: Fold the whipped cream (or whipped topping) into the lemon mixture in two additions until light and uniform. Don’t deflate it.

Layer the base: Line a 9x13-inch pan with a single layer of graham crackers, breaking pieces to fill gaps.

Add filling: Spread half of the lemon cream over the crackers. Top with another full layer of crackers. Spread the remaining lemon cream. Finish with a final layer of crackers.

Whisk the glaze: Mix powdered sugar, melted butter, and 2 tablespoons lemon juice until pourable and smooth. Add the remaining lemon juice if needed. It should ribbon off a spoon.

Top and chill: Pour the glaze over the final cracker layer, smoothing to the edges. Cover and refrigerate at least 6 hours, ideally overnight, until the crackers soften and the cake sets.

Serve: Slice with a sharp knife. Wipe the blade between cuts for clean layers. Garnish with extra zest or thin lemon slices if you like.