Combine warm water (finger temperature), half the sugar and 4 tablespoons of butter. Stir in the yeast. Let stand for 10 minutes, or until foamy (see notes).
In a large bowl, stir together the flour and salt. Mix in the the yeast mixture and mashed auyama. Mix in the mixer using the hook at medium-low heat for 5 minutes. Turn off the mixer and cover the bowl with a clean tea towel. Let it rest for an hour, or until the dough doubles in volume.
Start the mixer again over low speed, stir in raisins until it's well mixed, but be careful not to overwork the dough.
Grease a 6-cup non-stick bundt mold with the remaining butter. Sprinkle the bottom with the sugar, followed by the cinnamon powder. Pour the dough into the bowl. Cover and let it rest in a warm place until double in size, about 1 hour.
Preheat oven to 375 ºF [190 ºC].
Bake for 20 to 25 minutes in the preheated oven, or until you poke with a skewer and it comes out clean. Cool for 5 minutes before removing from the mold.
Notes
Please read this about yeast and bread-making. The water should be at 105 ºF [40 º C] and feel neither cold, nor hot. Too hot and the yeast will die. Too cold and it will take more time to start doing their work.