Whisk together flour, brown sugar, and salt for streusel.

Drizzle melted butter over flour mixture and combine with a fork.

Add almonds and raspberries to the streusel mixture.

Squeeze the mixture into large clumps.

Preheat oven to 350°F.

Butter and line an 8-inch square baking dish.

Whisk together flour, salt, and baking powder for the cake.

Beat butter and granulated sugar until fluffy.

Beat in the egg and vanilla.

Add half of the flour mixture and beat to combine.

Beat in the buttermilk.

Beat in the remaining flour mixture.

Fold in the remaining raspberries.

Transfer batter to the prepared pan.

Smooth the top of the batter.

Top with the streusel mixture.

Bake until a toothpick inserted into the center comes out with moist crumbs attached (about 30 minutes).

Transfer the cake to a rack to cool completely.

Lift the cake out of the pan using the parchment overhang.

Transfer to a cutting board or serving plate.

Cut into 16 pieces and serve.