1 3/4 cups all purpose flour
1/2 cup brown sugar
1/2 cup sugar
1/2 tsp ground cinnamon
1 tsp baking powder
1/2 tsp baking soda
1/2 tsp salt
1/2 cup butter, room temperature
3/4 cup milk
1 large egg
1 cup crunchy peanut butter, room temperature
1. In a large bowl, whisk the flour, brown sugar, sugar, cinnamon, baking powder, baking soda and salt. Beat in softened butter until the mixture resembles wet sand. Remove 3/4 cup of the mixture to a medium bowl and set aside.
2. Add milk and egg to the large bowl with the remaining flour mixture. Mix well, until no streaks of flour remain. Do not over-mix. Pour into prepared pan.
3. Add peanut butter to medium bowl with the remaining 3/4 cup flour mixture. Mix well and crumble (or drop in clumps, as the mixture will be thick) onto the cake batter in the pan.
4. Bake in preheated oven at 180 C for about 30 minutes, until a tester inserted into the center of the cake comes out clean. Cool on a wire rack before slicing.