Place the golden raisins in a small bowl and soak them in rum (or water) for 2 hours. Afterward, drain the raisins well, making sure to reserve the rum for later (to make the glaze). Set the raisins aside.
In a medium saucepan over medium-low heat, combine the milk, oil, eggs, and sugar. Warm the mixture on the stove, stirring constantly, until it reaches 98°F (warm to the touch but not too hot). Do not overheat. Remove the pan from the heat and add the yeast, stirring until some of the yeast dissolves.
Sift the flour into a large mixing bowl and add the warm milk-oil-egg-sugar mixture. Using a rubber spatula or wooden spoon, stir the batter, then mix in the raisins and black cumin seeds. The dough will be a little sticky. Do not overmix the dough, or it will become too tough, resulting in a dense and hard cake once the Babka is baked (though still edible).
Cover the bowl with a kitchen towel or plastic wrap and place it in a warm spot. Let it rise for 1 hour, or until it doubles in size. Make sure the dough is not in a drafty spot in your kitchen.
Once the dough has risen, bring it back to the kitchen counter and, with a clean hand, punch down the middle to let some of the gases escape from the dough.
Butter the 10-cup Bundt pan or babka pan, then sprinkle it with flour or powdered sugar.
Scoop the batter into the prepared baking pan. Cover the pan with a kitchen towel and let the dough rise in a warm place for an additional 30 minutes or until doubled in size. Preheat your oven to 330°F.
Place the Babka in the preheated oven and bake for 15 minutes. Then, cover the top of the pan with aluminum foil to prevent burning (do not remove it from the oven). Bake the Babka for an additional 35 minutes. The Babka should be golden, and a cake tester should come out clean.
Remove from the oven and let the Babka cool in the baking pan for 15-20 minutes. Then, transfer the Babka to a plate and let it cool completely. Once cooled, dust with powdered sugar or drizzle with icing.
OPTIONAL: To glaze the Babka, sift 1 cup of powdered sugar into a bowl and stir in 1-2 tablespoons of the reserved rum (or lemon juice) until smooth and thick enough to pour. Drizzle over the top of the completely cooled Babka, allowing it to drip over the sides. Decorate with sprinkles or whatever you desire. Enjoy!