Prepare. If you have not done so, prepare your lemon curd. Also, preheat your oven to 350°F and line an 8 x 8” baking pan with parchment paper that hangs over the sides of the pan.
Dry Ingredients. In a medium bowl, use a whisk to combine together your flour, powdered sugar, cornstarch, and baking soda.
Wet Ingredients. In a large mixing bowl beat together your oil and applesauce until well incorporated. Then beat in the granular sugar and vanilla extract on low until well completely incorporated.
Combine. Scrape down the sides of your mixing bowl and then add the flour mixture from the second step the the mixing bowl. Mix the ingredients until just combined.
Bottom. Press ⅔rds of the dough mixture into the bottom of your prepared baking pan. You can use a small dough roller to help you even the layer out.
Curd. Evenly spread your curd over the bottom layer. You can use the backside of a spoon to help evenly spread the curd out.
Crumble. Use your hands to crumble the remaining dough over the curd to make a crumble layer.
Bake. Bake your lemon curd bars for 22-25 minutes or until the crumble topping begins to turn golden brown.
Set. Allow the curd bars to cool in the pan before using the parchment paper to lift them out and slice them into bars.