To start off, you'll need to prepare your streusel, which is a crumbly topping that will give your cake an extra crunch. Begin by sifting flour into a medium-sized bowl, then add in cold butter.

Use a pastry cutter to cut the butter into the flour until the mixture appears crumbly. Ideally, you should have pea-sized chunks of butter scattered throughout the mixture.

Stir in sugar and salt to add sweetness and flavor, then place the bowl in the refrigerator until you're ready to use it.

Preheat your oven to a temperature of about 350 F. To make sure that your cake doesn't stick, generously grease a round,10-inch springform pan with butter.

Next, you'll need to combine all your dry ingredients. Measure out the flour, baking soda, baking powder, and sea salt, then whisk them together in a separate bowl. Set this aside for later use.

In a different bowl, beat eggs and sugar on high speed until they become foamy and pale in color. This could take a few minutes, so be patient.

Once you achieve the desired consistency, reduce the mixer's speed to low and add vanilla for flavor and cooled liquid butter for smoothness.

Detach the mixing bowl from the mixer and add the flour mixture to it in three parts. Gently fold the batter after each addition to avoid deflating the air pockets in the batter. These air pockets are essential as they give the cake its light, fluffy texture.

Now, it is time to assemble your cake. Pour the batter into your prepared pan and make sure that it is evenly spread. Sprinkle fresh raspberries over the top of the batter, giving it a tangy, fruity flavor. Finally, sprinkle your chilled streusel on top for a sweet, crunchy finish.

Place your cake in the preheated oven and bake for about 25 to 30 minutes. You can check if it is done by inserting a toothpick into the center; if it comes out clean, your cake is ready. Once baked, allow your cake to cool in the pan for about 15 minutes.

After cooling, carefully remove the cake from the baking pan and transfer it onto a cake platter. Slice into desirable sizes and enjoy your homemade, delicious raspberry coffee cake!