Spray a bundt pan with cooking spray. I have also heard that brushing the inside of the pan with butter helps to remove the cake from the pan after baking.
Pour caramel into the bundt pan.
In a large bowl or stand mixer, mix the cake mix, water, oil, and eggs together until combined. Pour cake mix on top of the caramel in the bundt pan.
In a blender add all flan ingredients and blend for at least 1 minute until blended well.
Pour flan contents slowly and evenly over cake content in the bundt pan.To make this easier, pour the flan mixture slowly over a spoon
Carefully place the bundt pan into a larger pan that will accommodate the bundt pan and 1 inch of boiling water.
With cooking spray, spray a piece of foil and place sprayed side down onto bundt pan, securely tighten the foil around the top of the pan.
Bake in a preheated 350-degree oven for 1 hour and 20 min or until a toothpick inserted into the center comes out clean.
Place on a cooling rack and remove the foil. Cool to room temperature for about 1 hour. Then refrigerate, uncovered for at least 2 hours to eight hours.
To remove the cake from the pan, place a plate onto the pan and gently turn the plate and pan upside down. You may have to jiggle it a little.