Prepare the Raspberry Filling

1. Mix Ingredients: In a medium bowl, combine fresh raspberries, granulated sugar, cornstarch, and lemon juice. Gently toss to coat the raspberries without mashing them. Set aside.

Make the Cookie Dough

1. Cream Butter and Sugars: In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
2. Add Eggs and Vanilla: Beat in the eggs, one at a time, followed by the vanilla extract.
3. Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry mixture to the wet ingredients, mixing until just combined.

Prepare the Crumble Topping

1. Combine Topping Ingredients: In a medium bowl, combine flour, oats, brown sugar, melted butter, and cinnamon (if using). Mix until crumbly.

Assemble the Cookies

1. Preheat Oven: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
2. Form Cookies: Scoop about 1 tablespoon of cookie dough and flatten it slightly in your hand. Place a small spoonful of the raspberry filling in the center, then enclose the filling with the dough to form a ball.
3. Place on Baking Sheet: Arrange the cookie balls on the prepared baking sheet, leaving space between them.
4. Top with Crumble: Sprinkle the crumble topping generously over each cookie.

Bake

1. Bake the Cookies: Bake in the preheated oven for 20-25 minutes, or until the edges are lightly golden and the topping is slightly crisp.
2. Cool: Remove from the oven and let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.