At least 2-3 weeks in advance, chop all the dry fruits and place them in an airtight container, soaking them in required amount of Rum and 4 tbsp Caramel syrup.
For Caramel syrup, heat 4 tbsp sugar and 1 tsp of water on medium heat until the sugar melts and browns up. Take off the heat and carefully add the water and stir well and use.
In a sauce pan, take ½ cup sugar (100 grams) and 2 tbsp water. Mix and stir very well. keep this pan on the stove top on a low flame. Bring this sugar solution to a boil on a low flame.
You will see the mixture bubbling initially. continue to cook and do keep on stirring often. At one point it might look that the sugar is getting crystallized. Continue to cook and stir frequently.
The pale brown color is still there. continue to cook and stir and you will see the color changing to a dark brown. Remove the pan from the stove top and place it down. immediately add 1 cup water to the caramel.
Be careful while doing so as the mixture splutters. the caramel will harden as soon as you pour the water. keep the saucepan back on the stove top on a low flame. stir often and bring to a gentle simmer till all the hardened caramel is dissolved.
Do stir often so as to aid in dissolving the caramel. let this caramel solution cool completely. filter this solution and keep aside.
Preheat Oven to 160 degree and grease your Cake pan and cover the bottom and sides with greased parchment paper.
Sift together all the dry ingredients - Flour, baking powder, coffee,salt and Spices. Beat the oil with powdered sugar until smooth and creamy.
Add the whisked yogurt until well incorporated. Add in the dry ingredients slowly and mix until combined.
Add the Caramel syrup and smoothly combine everything together. Strain the rum soaked fruits (save the rum) , and coat them with some all-purpose flour to avoid the fruits from sinking to bottom of cake and add the fruits into the cake batter ,
Use a large wooden spoon to fold/mix the fruits into the cake evenly. Mix 1 tablespoon of vinegar to the warm milk and let it split. Add the baking soda to it and you will see it rising . immediately fold it into the batter and mix everything well.
Pour the cake batter into your prepared cake pan and bake for 55 to 60 minutes. Each oven is different, so do a cake test at 55 mins - insert a toothpick into the cake center If it comes out clean, the cake is ready.
After taking the cake out from the oven, pour 2-3tblsp of the saved rum over the cake. Allow the cake to cool for 15 mins and then flip the cake pan onto a wire-rack.
Once cooled release the cake from pan and brush the sweet rum (from the strained fruits) all over the cake.