My Pineapple Open Tarts won't dislodge from their moulds
If there is really no way to delicately take off the moulds, I'd suggest feezing them. Then once they've hardened, heat up the mould and try to push the tarts out/bang the mould on a hard (not fragile...) surface. They'll be hard enough so you can apply more force without breaking.

As a last resort... :)

Also, removing them right out of the oven might not be a great idea as they will often shrink while cooling down, which can help take them out. And as Fabby pointed out : butter AND flour.