For the Cake:

1. Preheat the oven to 375°F and liberally grease an 8 x 8-inch baking pan (or a 9-inch round cake pan). Line the pan with parchment paper so that there is a slight overhang on the edges (this makes for easy removal of the cake after baking).
2. Using a stand or hand-held mixer, beat together the butter and sugar until creamy and smooth, about 3 minutes.
3. Stir in the raspberry jam, egg, and vanilla and mix again to combine.
4. In a separate bowl, whisk together the flour, baking powder, and salt.
5. Stir the dry ingredients into the wet ingredients, mixing until just combined. Resist the urge to overmix – this will create a dense, tough cake.
6. Fold in the buttermilk until just combined.
7. Very gently fold in the raspberries – if they break up a bit, that’s okay. I try to keep them as intact as possible.
8. Spread the batter out evenly in the prepared pan.

For the Streusel:

1. Whisk together the flour, sugars, and salt.
2. Add the melted butter and stir the mixture until it clumps together and is crumbly.
3. Sprinkle the streusel over top of the coffee cake batter.

To Bake:

1. Bake the cake for 50-60 minutes or until the top is golden and the cake is set in the center (a toothpick inserted into the center comes out with only a few moist crumbs). Allow to cool in the pan slightly before slicing and serving.
2. This can be enjoyed warm or at room temperature.