Separate eggs, placing the whites in the bowl of a stand mixer and the yolks into a saucepan.
Add sugar, salt, and 1/3 cup plus 1 tablespoon flour to the yolks. Splash in about 1/4 of the milk and start blending mixture with a whisk. Pour in remaining milk and whisk until smooth.
Cook and stir mixture over medium heat until hot to the touch, occasionally dipping your finger in to test. Whisk constantly until custard is thick enough to form ribbons.
Remove custard from heat and add vanilla extract, banana liqueur, and cold butter. Whisk until butter dissolves. Set custard aside.
Preheat the oven to 400 degrees F (200 degrees C).
Toss banana slices with lemon juice.
Spread a quarter of the custard over the bottom of a baking dish. Add a single layer of vanilla wafers. Cover with 1/2 of the bananas and spread 1/2 of the remaining custard on top. Add another layer of vanilla wafers, using slightly fewer this time. Top with the remaining bananas and custard. Smooth the top and tap dish against the counter to settle the pudding.
Add cream of tartar to the egg whites. Beat using the whisk attachment until foamy. Gradually add sugar and beat until stiff, but not dry, peaks form. Spread meringue over the pudding using a soft spatula, creating ridges for contrast.
Bake in the preheated oven until meringue is nicely browned, 7 to 10 minutes. Serve warm or chilled.