For the crumble and base -
1 cup rolled oats
2/3 cup flour
1/4 cup light brown sugar
1/2 tsp cinnamon
6 tbsp butter, cubed and chilled
For the raspberry filling -
8 ounces raspberries, fresh or frozen
1 tbsp honey, maple syrup, or sugar
1/2 tsp vanilla
Zest of one lemon
1 tbsp lemon juice
1 tbsp cornstarch or flour
1) To a blender, add the oats, flour, brown sugar, cinnamon, and cubed butter. Gently pulse to combine, but you don't want a fine powder. You want the oats to be chopped into small bits, but no further.
2) Empty the oat mixurte from the blender into a small bowl, and work the butter into the mixutre with your fingers, just until barely combined. Set this aside to chill in the fridge.
3) To make the raspberry filling, add the raspberries, sugar, vanilla, lemon juice, and zest to a small pan. Heat over medium-high heat to bring to a boil, and occasionally stir and scrape the bottom to prevent sticking. When the mixture comes to a bowl, let it continue to bubble and thicken for 3-5 more minutes.
4) Remove the pan from the heat, and add in the flour, stir to combine. Set this aside to cool.
5) Preheat your oven to 375°F.
6) Using a pyrex or baking dish, press 2/3 of the oat mixture in the bottom of the dish. Press it down solid in a layer about 1/4 inch thick.
7) Spread the raspberry filling on top of the oat base in an even layer.
8) Then, crumble the remaining oat mixture on top in an even layer. Bake for 20-25 minutes, or until golden brown on top. Remove it from the oven to cool.
9) Slice into bars within the pan, roughly 6-8 bars or larger, and enjoy! Serve with ice cream or just by themselves!