• Preheat oven to 325 degrees. Place rack in middle of oven. Spray a 9x9-inch baking dish with nonstick cooking spray. Set aside.

Crust

• In a medium bowl, whisk together flour, cinnamon and salt. Set aside. In the bowl of a stand mixer fitted with a paddle attachment, combine butter and sugar. Beat at medium speed until well blended, about 1-2 minutes, scraping down the sides of the bowl as needed. Slowly add the flour mixture and mix just until incorporated. Press the dough into the bottom and 1/2 inch up the sides of the prepared pan.

Filling

• Spread the 3/4 cup of the apricot preserves over the crust.

Topping

• In the bowl of the stand mixer fitted with the paddle attachment, combine flour, sugar, cinnamon and salt until well combined. Add butter and mix until mixture resembles large crumbs. Add chopped walnuts. (I like to use my fingers to fully crumb the mixture together.)
• Sprinkle the streusel mixture evenly over the preserves. Bake for 55-60 minutes until lightly browned and the preserves appear to be bubbling. Transfer to a wire rack to cool for about 5 minutes, then cut into 16 bars, but leave in pan. Let cool to room temperature, about 1 hour. 
• Bars can be stored in a airtight container at room temperature for up to 4 days.