Preheat the oven to 180 ºC. Grease a 22cm Bundt pan with a little butter.
In a bowl, mix all the dry ingredients: flour, baking powder, baking soda, salt, and ground spices. Set aside.
Mix the yoghurt with 4 tablespoons of warm water and set aside.
In another bowl put the brown sugar and the white sugar. Add the eggs one by one and whisk them for 2-3 minutes until foamy.
Add pumpkin puree and mix at medium power.
Add oil and mix until it is well integrated. Add the yoghurt and water mixture.
Add the flour mixture and whisk until completely combined.
Add walnuts and raisins. Mix.
Pour the mixture into the pan, bake at 170 ºC for 45-50 minutes. After 45 minutes, insert a toothpick to see if it comes out clean. If not let it bake for another 5-7 minutes.
Let it cool completely before removing from the pan and sprinkle with icing sugar.