140g all purpose flour

45g buckwheat flour

1 tsp baking powder

1/2 tsp baking soda

250g greek yogurt or sour cream

145g unsalted butter, softened

230g sugar, divided

2 tsp vanilla

2 eggs

1 cup blueberries

1 1/2 cup sliced rhubarb

For the crumble

80g flour

80g ground almond or walnut

80g brown sugar

80g chilled unsalted butter

1 tsp cinnamon

1 tsp cardamom

1/4 tsp salt

Preheat oven to 350
To make the crumble, finely dice the butter. Combine the remaining ingredients in a bowl. Using your fingertips work the butter into the mixture until evenly mealy. Place in fridge while you make the rest of the cake
Mix the rhubarb and blueberries with 30g of sugar, set aside
In the bowl of a stand mixer fitted with the paddle attachment, beat butter with remaining sugar and vanilla until fluffy.
Add in eggs and continue to beat until light and fluffy
Add in flour, baking soda and powder and mix on slow. Add in sour cream and stir until just combined
Transfer to a greased baking dish. Top with fruit, then sprinkle crumble over, bee for 20 wish minutes