01 -
Heat oven to 180°C / 350°F. Line a 20 cm square metal baking pan with baking paper, leaving an overhang.
02 -
Mix flour, oats, brown sugar, baking powder and salt. Stir in melted butter until evenly moistened and clumpy.
03 -
Press two-thirds of the mixture firmly into the pan. Bake 12 minutes while preparing the filling.
04 -
Gently toss raspberries with white sugar, cornstarch and lemon juice. Spread evenly over the hot base. Scatter the remaining oat mixture over the fruit in loose clumps.
05 -
Bake another 25–30 minutes until the topping is golden and the raspberry filling bubbles visibly near the center as well as the edges.
06 -
Cool in the pan at least 60 minutes before lifting out and cutting into 12 bars. Warm bars will be softer and more likely to crumble.
07 -
Once cool, refrigerate covered for up to four days. Keep chilled for tidy slices; bring a portion to room temperature before eating if preferred.