Heat oven to 375 degrees. Line bottom of pan with foil and spray foil with nonstick cooking spray.
Mix flour, granulated sugar and salt with low speed until combined for 5 seconds. On low, add butter a tablespoon at a time. Mixture should resemble damp sand.
Measure 1.25 c above mixture into medium bowl and set aside. distribute remaining flour mixture evenly in bottom of prepared baking pan; press mixture into an even layer to form a bottom crust. Bake until edges begin to brown 14 to 18 minutes.
Create streusel: Add brown sugar, oats, and nuts to reserved flour mixture; toss to combine. Work in remaining 2 tbsps butter by rubbing mixture between fingers until butter is fully incorporated.
Combine preserves, raspberries and lemon juice in small bowl; mash with fork until combined but some berry pieces remain.
Spread filling evenly over hot crust; sprinkle streusel topping evenly over filling. Bake for 22-25 minutes.
Cool to room temperature and remove from baking pan. Cut into squares with a chef's knife.
mark.goadrich