1/2 cup (125 mL) butter, softened
1 cup (250 mL) packed brown sugar
1 tsp (5 mL) vanilla
2 cups (500 mL) all-purpose flour
1 tsp (5 mL) baking soda
1 tsp (5 mL) baking powder
1/2 tsp (2 mL) salt
1 cup (250 mL) buttermilk
2 cups (500 mL) chopped rhubarb
1/2 cup (125 mL) packed brown sugar
1/4 cup (50 mL) chopped hazelnuts or sliced almonds
1 tbsp (15 mL) all-purpose flour
1/2 tsp (2 mL) cinnamon
2 tbsp (25 mL) butter, melted
Grease 9-inch (2.5 L) springform pan; set aside.
In bowl, combine brown sugar, chopped hazelnuts, flour and cinnamon. Using fork, stir in butter until crumbly; set aside.
In large bowl, beat butter with brown sugar until light and fluffy; beat in eggs, 1 at a time. Beat in vanilla.
In separate bowl, whisk together flour, baking soda, baking powder and salt. Add to butter mixture alternately with buttermilk, making 3 additions of flour mixture and 2 of buttermilk. Fold in chopped rhubarb. Scrape into prepared pan; sprinkle with topping.
Bake in centre of 350°F (180°C) oven until cake tester inserted in centre of cake comes out clean, about 1-1/4 hours. Let cool in pan on rack for 5 minutes. Remove side of pan. Serve warm or cool.