Mix the filling ingredients in a large bowl and set aside
Make the crust and topping
Place the softened butter in the bowl of a stand mixer, or in a large mixing bowl if using a hand mixer.
Add the sugar and beat until the mixture lightens in color and becomes fluffy.
With the mixer running, add the eggs, one at a time, beating until each one is completely incorporated.
Beat in the vanilla and the lemon zest.
Put the salt and baking powder in, plus one cup of the flour and beat until thoroughly mixed.
Mix in the remaining two cups of flour, until well combined.
Make the bars
Preheat the oven to 350°. Generously butter the baking sheet, making sure to get in the corners, so you don't have any sticking later on.
Spread just a bit over one half of the crust/topping mixture in the bottom of the pan. It is going to be a thin layer, but make sure the entire bottom of the pan is covered.
Spread all of the apple mixture in an even layer over the crust layer.
Use a teaspoon and your finger to put small dabs of the topping over the apples. Try to get it evenly distributed, but not a solid layer. You want small areas of apple showing through.
Place in the preheated oven, and bake for around 50 minutes, until the apples are a bit bubbly and the top layer is nicely brown. Turn the pan a couple of times during baking, to ensure it bakes evenly.
Remove the pan to a cooling rack. Allow it to sit for about 1/2 hour before slicing into bars.
Mix the lemon juice and 10X sugar together until they smooth. Drizzle this over the top of the bars before serving. If you plan to serve it the next day, you can wait to add the drizzle until then.
Notes
If you printed the recipe, you can scan this QR code to find it again for tips and more details:These bars should be stored in the refrigerator, because the moisture from the apple could cause them to spoil rather quickly. Use a container with a tight lid to keep them fresh. They can be frozen and defrosted.