Commonly known as annatto seed in the States, the correct term for the seeds of an annatto tree is achiote seeds. Native to South America, they have been used to color food and cosmetics. These seeds have a peppermint scent and a slightly peppery taste with just a hint of bitterness.
The seeds can be ground and added to soups and stews or made into a paste to be spread on fish or pork before grilling. It's a tough process to work with annatto, as the dried seeds are very hard and quite difficult to grind.
To make paste:
Cover seeds with water and bring to a boil. Simmer over moderate heat for 3 minutes. Remove from heat and let stand for a couple of hours. Drain and pat dry using a paper towel so as to not stain a clothe one. Transfer to a mortar and pestle or spice grinder and grind to a paste.