Whisktogether the flour, brown sugar, and cinnamon. Then blend – the butter into the mixture with your fingers and use a spatula to mix it into a sandy, clumpy consistency.
Blend the butter into the mixture with your fingers and use a spatula to mix it into a sandy, clumpy consistency. Add the eggs, one at a time, mixing between each addition
Add the cake batter to the prepared pan and drop dollops of blueberry jam on top. Swirl the jam through the cake with a knife and cover it with streusel topping.