Preheat oven to 350F. Grease and flour a 9x5 loaf pan.
Whisk the melted butter, buttermilk (in my case water+buttermilk powser), tahini, and eggs together in a large bowl.
Whisk both sugars, the 185g cake flour, baking powder, and salt together in a separate large bowl.
Pour the wet into the dry and whisk until there are no lumps left.
Toss 1 cup of the brittle with teaspoon and a half of flour, then mix it into the batter.
Pour the batter into the loaf pan and sprinkle the rest of the brittle over the top.
Bake for 60 minutes. If the cake is still jiggly bake for up to 10 minutes more. It should be somewhat firm and spring back when you touch it.
Let the cake cool at least 45 minutes in the pan before you remove it or you will end up with a broken mess.After 45 minutes you can remove it and let it cool completely on a cooling rack.