The sponge mixture is prepared with rapeseed oil instead of butter: This provides us with omega-3 fatty acids. They are essential for the body, i.e. it cannot produce them itself but must absorb them through food. In addition, rapeseed oil provides a large portion of cell-protecting vitamin E.
If you want to bake vegan, you can replace eggs with soy flour (3 tablespoons of soy flour mixed with 9 tablespoons of water) and buttermilk with vegetable drink (e.g. soy or almond based). If you still don't want to do without the golden yellow colour of the cake, you can also replace it with vegetable drink. You can do this with a little saffron or turmeric.
Rinse and dry rhubarb, cut into 1.5 cm (approximately 1/2 inch) pieces.
Beat butter with sugar until creamy, add eggs gradually. Combine flour with baking powder. Add flour and milk, alternately, to butter mixture. Sprinkle rhubarb with flour and fold into batter.
Spread batter in a lined with baking paper square baking dish, sprinkle with pistachios and hazelnuts and bake in preheated oven at 180°C (approximately 350°F) for 45-50 minutes (inserted toothpick should come out clean).
Remove cake from oven and cool slightly. Remove from pan and cool on a wire rack. Sprinkle with remaining nuts, cut into slices and serve, if desired, with rhubarb compote.