Method
1. Add cake flour, granulated sugar, dark brown sugar, ground cinnamon and coarse grey sea salt to a clean medium bowl
2. Mix briefly until just combined
3. Pour unsalted butter into the topping
4. Mix until coarse crumbs form then set aside
5. Pre-heat oven - 160°C
6. Grease a clean baking pan then set aside
7. Add cake flour, baking soda and coarse grey sea salt to a clean medium bowl
8. Whisk together then set aside
9. Add unsalted butter and granulated sugar to a clean stand mixer bowl
10. Beat until light and fluffy - approx 2 min, medium speed
11. Mix in egg and egg yolk to the batter one by one
12. Mix in vanilla extract to the batter
13. Mix in one third of dry ingredients to batter
14. Mix in cultured lowfat buttermilk to the batter
15. Mix in one third of dry ingredients to batter
16. Mix in cultured lowfat buttermilk to the batter
17. Mix in the rest of dry ingredients to batter
18. Beat until well combined
19. Spoon batter into baking pan
20. Spread evenly
21. Spread with jam
22. Transfer topping to baking pan
23. Bake until golden brown - approx 1 hr, 160°C
24. Let cool slightly on round wire rack - approx 15 min
25. Dust with powdered sugar
26. Serve