Preheat the oven to 350 degrees.
Bring one cup of sugar to a boil.
Add one cup of pineapple chunks to the sugar mixture, and cook for 3-5 minutes.
Once the sugar mixture is thickened, remove from heat and carefully coat the bottom of the baking dish making sure to spread pineapple chunks around the dish evenly.
In a blender, combine the sweetened condensed milk, evaporated milk, eggs and vanilla and blend until smooth.
Pour mixture into pan and cover with aluminum foil. Bake at 350 degrees for 90 minutes.
Remove from oven and allow to fully cool. When ready to serve, run a small knife along the edge of the flan to loosen.
Carefully invert onto a serving plate by shaking gently to release the flan. The caramel side should be on top. Garnish with cooked pineapple to finish.