2½ cups all-purpose flour
2/3 cup granulated sugar
½ teaspoon salt
1 cup plus 2 tablespoons unsalted butter, divided, cut into ½-inch pieces and at cool room temperature
¼ cup light brown sugar
½ cup old-fashioned rolled oats
½ cup (2 ounces) pecans, chopped fine
¾ cup (8½ ounces) raspberry preserves
¾ cup (3½ ounces) fresh raspberries
1 tablespoon lemon juice
1. Preheat the oven to 375 degrees F. Line a 9x13-inch pan with foil so it hands over the edges. Spray the foil-lined pan with nonstick cooking spray.
2. In the bowl of a stand mixer fitted with a paddle attachment, mix the flour, granulated sugar and salt at low speed to combine, about 5 seconds. With the machine on low, add 1 cup of the butter, 1 piece at a time, then continue mixing on low until the mixture resembles damp sand, 1 to 1½ minutes. (If using a food processor, process the flour, granulated sugar, and salt until combined, about 5 seconds. Scatter the 1 cup of butter pieces over the flour mixture and pulse until the mixture resembles damp sand, about twenty 1-second pulses.)
3. Measure 1¼ cups flour mixture into a medium bowl and set aside; distribute the remaining flour mixture evenly in the bottom of the prepared baking pan. Using your fingers or the bottom of a measuring cup, firmly press the mixture into an even layer to form the bottom crust. Bake until the edges begin to brown, 14 to 18 minutes.
4. While the crust is baking, add brown sugar, oats, and nuts to the reserved flour mixture; toss to combine. Work in the remaining 2 tablespoons of butter by rubbing the mixture between your fingers until the butter is fully incorporated. Pinch the mixture with fingers to create hazelnut-sized clumps; set streusel aside.
5. Combine preserves, raspberries, and lemon juice in a small bowl; mash with a fork until combined but some berry pieces remain.
6. Spread the filling evenly over the hot crust; sprinkle the streusel topping evenly over the filling (do not press streusel into filling). Return the pan to the oven and bake until the topping is a deep goldne brown and the filling is bubbling, 22 to 25 minutes. Cool to room temperature on a wire rack, 1 to 2 hours; remove from the baking an by lifting the foil extensions. Cut into squares and serve. The bars can be stored in an airtight container at room temperature.
*Note #1: Frozen raspberries can be substituted for fresh; be sure to defrost them before combining with the raspberry preserves.
*Note #2: If your fresh raspberries are very tart, add only 1 or 2 teaspoons of lemon juice to the filling.