Preheat oven to 425º F.
Pat the salmon dry and season with salt and pepper. Line a baking sheet with aluminum foil and grease with some oil. Place the salmon on the baking sheet skin-side down.
Add the orange and grapefruit juice to your blender along with the Achiote paste, garlic, oregano, and salt. Process until you have a smooth puree.
Brush some of the sauce over the salmon using a pastry brush. Marinate for 15 minutes at room temperature.
After this time has passed, brush the salmon again with more Achiote marinade. Place in the oven and roast for 10-12 minutes.
