1. Soak it for 2-3 hours first. Then cook it, and it'll stink.
2. Or soak the lotus seeds for a while (about 10- 15 minutes), put them in the pressure cooker and adjust them to the cooking stall (10- 15 minutes).
In addition: lotus seeds will be bitter if they are not cored, but they will have a mild effect. I usually remove them when I eat them.