Preheat oven to 350°F. Line a 9-inch round cake pan with parchment paper.
Combine topping ingredients and mix until a chunky dough forms. Set aside.
In a small bowl, combine flour, baking powder, baking soda and salt; set aside.
In a large bowl, cream together butter and Bob’s Red Mill Coconut Sugar until light and fluffy, about 5 minutes with an electric mixer. Add egg and vanilla and mix until combined.
Add dry ingredient to sugar mixture, alternating with buttermilk, until a smooth batter forms.
Spread batter into prepared cake pan and sprinkle topping evenly over the cake. Bake until a tester comes out clean, 50 – 55 minutes.