Preheat your oven to 350º F and line a 8×8 pan with parchment paper.
Place the saltines in a large plastic bag and beat with a rolling pin until a chunky crumb forms. Combine in a bowl with butter and sugar and mix with your hands until large clumps form.
Pat the saltine crust into your pan and press it down evenly with the back of a measuring cup. Bake for 12-15 minutes until lightly golden. Let cool to room temperature.
While crust cools, whisk the sweetened condensed milk and egg yolks together. Add the lemon juice, baking powder, and flour and whisk thoroughly until no white streaks remain.
Pour the lemon custard into your pan and bake for another 12-15 minute until there is little to no jiggle in the middle. Let chill in the fridge for 2 hours.
Slice bars into 9 squares and place prepared Italian meringue into a piping bag fitted with a round tip. Pipe squiggles of Italian meringue onto each bar and torch with a kitchen torch until the tops are golden brown. (These bars will still be delicious untorched).