Olive Oil Cake with Brown Butter Frosting

Method

1. 1
   Preheat the oven to 350°F and place a rack in the center of the oven.
2. 2
   In a large bowl, add the 300 grams of granulated sugar, the zest of one and a half lemons and one orange. Rub the zest into the sugar with your fingers until fully incorporated. The sugar will begin to clump from the oils.
3. 3
   Crack all five eggs into the bowl, along with the sour cream, olive oil, vanilla, and salt. Whisk for about two minutes until light and fluffy.
4. 4
   Sift the flour, baking soda, and baking powder into the wet ingredients. Use a flat rubber spatula to fold the dry ingredients into the wet until just combined. It will still look lumpy from the bubbles.
5. 5
   Grease a 9" round cake pan. *I'm using this 9" springform pan from USA pan that I love, you don't need to line or grease the pan.
6. 6
   Pour the cake batter into the pan and bake in the hot oven for 30 minutes. After 30 minutes, rotate the cake 180 degrees and bake for another 20-30 minutes until golden brown and a toothpick inserted into the center comes out clean.
7. 7
   Once baked, take the cake out of the oven and leave to cool for at least 15 minutes before removing it from the cake pan and leaving it to cool completely.
8. 8
   While the cake bakes and cools, place the butter into a sauce pot. Place the pot over medium low heat and let the butter melt, then bubble, then go silent. Once it quiets down, start to stir it regularly until it really begins to brown.
9. 9
   Once it has browned, pour your butter into a heat-safe mixing bowl and leave to cool to room temperature. You want the butter to become the texture of just softened butter, not soup. If it isn't firming up enough, place the bowl of butter into the fridge, stirring occasionally until it's just spreadable.
10. 10
    Sift the powdered sugar into the bowl with the butter and add the teaspoon of vanilla extract. Use a mixer to whip until fully combined and smooth. Add in a tablespoon of heavy cream at a time until the buttercream is soft and spreadable and no longer super stiff.
11. 11
    If you add too much cream, just add in a bit more powdered sugar until it is thick enough.
12. 12
    Once the cake has cooled and the buttercream is whipped, scoop the frosting onto the top of the cake.
13. 13
    Use the back of a spoon to swirl it around for a rustic design or an offset spatula to smooth it over the top and sides of the cake. I like to use a bench scraper last to really smooth out the sides.
14. 14
    Store in the fridge fully iced on a plate or cake stand. Once you've cut into it, store the cake in an airtight container in the fridge.