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1
Make the crust and crumb: Preheat the oven to 350F Butter the bottom and sides of a 9-by-13-inch glass or light-colored metal baking pan.
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2
Put a long piece of parchment paper in the bottom of the pan, letting the parchment extend up the two short sides of the pan and overhang slightly on both ends.
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3
Butter the parchment.
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4
Put the flour, brown sugar, oats, salt, baking powder, baking soda, and cinnamon in a food processor.
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5
Pulse in short bursts until combined.
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6
Add the butter and pulse until loose crumbs form.
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7
Reserve 1 to 1 1/2 cup of the mixture and set aside.
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8
Pour the rest of the mixture into the prepared pan and use your hans or the back of a large wooden spoon to push the crust into an even layer at the bottom of the pan.
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9
The crust should touch the sides of the pan.
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10
Bake until golden brown, 12 to 15 minutes.
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11
Transfer to a wire rack and let the crust cool.
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12
Keep the oven on while you make the raspberry filling.
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13
Make the raspberry filling: In a medium bowl, whisk the sugar, lemon zest, cinnamon and flour together.
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14
Add the raspberries, lemon juice and butter and use your hands to toss gently until the raspberries are evenly coated.
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15
Assemble and bake the bars: Spread the raspberry filling evenly on top of the cooled crust.
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16
Sprinkle the reserved crust mixture evenly on top of the filling.
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17
Bake for 35 to 45 minutes, rotating the pan every 15 minutes, until the top is golden brown and the filling starts to bubble around the edges.
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18
Transfer to a wire rack to cool completely, then cut into squares and serve.
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19
The bars can be stored in the refrigerator in an airtight container for up to two days.
