Zucchini and Hazelnut Cake with Brown Butter Frosting

Ingredients:
Cake:
2 cups flour
1/3 cup hazelnut flour
1 tsp baking powder
1 tsp baking soda
1/2 tsp salt
1/2 tsp cinnamon
2 large eggs
3/4 cup sugar
1/4 cup dark brown sugar
1/2 cup olive oil
1/3 cup orange juice
1 1/4 cup shredded zucchini, pat dry
Frosting:
2 sticks butter, browned
1 lb powdered sugar, sifted
1 tsp vanilla extract
1/2 tsp salt
2 tbsp milk
Directions:
In a small saucepan over medium heat, bring butter to a simmer, stirring occasionally. Let cook until butter foams, then brown bits form, about 5-7 minutes. Remove from heat and let come to room temperature (2-3 hours, depending on how warm the room is) in order to properly use for
frosting.
When butter is the correct temperature, add to the bowl of a stand mixer with whisk attachment. Add butter and whisk until aerated, about 2 minutes. Add vanilla extract and slowly add powdered sugar and salt. Lastly, add milk and beat just until combined. If piping frosting, transfer to a piping bag with desired tip.
Cake:
Preheat an oven to 350 degrees. In the bowl of a stand mixer with paddle attachment, add eggs and sugar, beating to combine. Pour in olive oil and orange juice and combine. In a separate bowl add both flours, baking powder, baking soda, salt and cinnamon. Stir to combine, then slowly add to mixer on medium speed, just until combined. Fold in zucchini.
Grease an 8x8 pan with butter and flour (or baking spray) and pour batter in, smoothing to an even layer. Bake for 30-35 minutes. Let cool completely and top with frosting.