½ cup (65 g) unsalted pistachios, lightly roasted and finely chopped in a food processor
2 tsp baking powder
1/2 cup (115 g) unsalted butter, softened
1/2 cup (125 ml) milk
In a bowl, combine the rhubarb with ¼ cup (55 g) of the sugar. Let rest for 1 hour at room temperature.
With the rack in the middle position, preheat the oven to 350°F 180°C). Line a 5 x 9-inch (13 x 23 cm) loaf pan with a strip of parchment paper, letting it hang over two sides. Butter the other two sides. Set aside.
In a bowl, combine the flour, pistachios and baking powder.
In a large bowl, cream the butter with the remaining sugar using an electric mixer. Add the eggs, one at a time, and beat until smooth. At low speed, add the dry ingredients alternately with the milk. With a spatula, add the rhubarb and its juice. Stir to combine.
Spoon into the prepared pan and bake for 1 hour or until a toothpick inserted into the centre of the cake comes out clean. Let cool. Remove from the pan and let completely cool on a wire rack.