Preheat your oven to the specified temperature and prepare a cake pan by greasing it.
In a mixing bowl, cream together butter and sugar until light and fluffy.
Add eggs one at a time, beating well after each addition. Mix in lemon zest, lemon juice, and vanilla extract.
In a separate bowl, whisk together flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, alternating with buttermilk, beginning and ending with the dry ingredients. Mix until just combined.
Pour the batter into the prepared cake pan, spreading it evenly.
In a small bowl, mix together the ingredients for the crumb topping until they resemble coarse crumbs. Sprinkle the topping over the batter.
Bake in the preheated oven for the specified time or until a toothpick inserted into the center comes out clean.
Once baked, remove from the oven and let the cake cool in the pan for a few minutes. Then transfer it to a wire rack to cool completely.