Preheat oven to 325 degrees F. Lightly grease 9x9-inch cake pan.

In mixing bowl, whisk together eggs, oil, water and vanilla extract.

Add all flours, coconut sugar and baking soda and stir until well combined. Pour into cake pan.

Bake 30-35 minutes, until toothpick inserted in center comes out clean. Let cake cool or place in freezer to accelerate cooling.

For crumble, in blender, mix coconut sugar, hazelnuts and flour until it has consistency of flour. (Note: Some larger chunks of hazelnut are fine.)

To brown butter, in saucepan over medium heat, add butter and bring to boil, letting it bubble 30 seconds prior to removing from heat. (Note: Butter will smell nutty when browned. Do not boil too long as butter will burn.)

In bowl, add crumble mixture and stir in browned butter until well combined.

For caramel, in bowl, combine all ingredients and mix until smooth.

Spread thin layer of caramel over cooled cake and evenly sprinkle on crumble.