In a large mixing bowl, combine flour, oats, brown sugar, baking powder and salt, mix until well combined

Next, pour in melted butter, and add vanilla extract. Stir mixture with a spatula or wooden spoon until if forms a crumbly texture, you want it moist but still crumbly, so dont overmix

Preheat oven to 350° F

In a medium bowl, add fresh raspberries, sprinkle cornstarch over raspberries and add lemon juice and sugar. Gently toss together, careful to not crush berries too much. Set aside

Grease an 8x8 baking dish, take 2/3 of the crumbly mixture and press firmly into bottom of dish.

Pour raspberry filling over crust, spreading evenly.

Sprinkle remaining crumb mix over top of raspberry filling.

Bake for 30-35 min, or until top is golden brown and filling is bubbling lighting around edges. Allow to cool completely before cutting into squares. Top with a sprinkling of powdered sugar once cool and enjoy!