Grease the bottom and sides of a 9 x 13-inch glass or light-colored metal pan. Insert a long piece of parchment paper into the bottom of the pan, allowing the paper to extend over both short sides to ease removal of the bars.
In a food processor, combine the flour, sugar, oats, salt, baking powder, baking soda, and cinnamon. Pulse in short bursts until the ingredients are combined. Add the butter, and pulse until the mixture is crumbly and has a powdery texture.
Put aside 1 1/2 cups (375 ml) of the mixture to spread on top of the bars.
Pour the remaining mixture into the pan. Use your hand or the back of a large wooden spoon to spread the batter into an even layer until it comes up against the sides of the pan.
Bake for 12 to 15 minutes or until golden brown. Transfer the pan to a wire rack and allow it to cool.
Keep the oven at the same temperature.
For the raspberry filling:
In a mid-sized bowl, mix the sugar, lemon zest, cinnamon, and flour. Add the raspberries, lemon juice, and butter, and carefully mix with your hands until the raspberries are well coated.
Assembling and baking the bars:
Spread the raspberry filling evenly over the cooled crust. Spread the remaining mixture uniformly over the raspberry filling.
Bake for 35 to 45 minutes, until the top is golden brown.
Place the pan on a wire rack and let cool completely. Cut the batch into 24 portions, and serve.
The bars can be kept in the refrigerator in an hermetically sealed container for one week.
