Dissolve achiote paste in orange juice, then marinate fish in the mixture.
Cube half the pineapple; cook over high heat, stirring constantly until juicy, then reduce to medium. When the sauce turns dark yellow, add sugar, lemon juice, and water and boil 5 minutes. Blend in cubes of butter. Strain and return to medium heat until the sauce thickens; set aside.
Cut tortillas into to short, thin strips then fry them in oil. Place on paper toweling to absorb excess oil.
Blanch cilantro, towel dry then puree with onion, chile and salt to taste.
Saute fish in butter over medium heat until flaky. Serve with tortilla strips, diced pineapple, cilantro paste, and pineapple sauce.