Place the ground coriander, salt, turmeric and cayenne in a small mixing bowl.
Use a fork to stir in 1/2 cup water to form a thin paste.
Heat the oil in a large skillet over medium-high heat.
Add the onion and cook, stirring often, until onions begin to turn pale caramel at the edges, about 4 minutes.
Add the spice paste and cook, stirring, until the oil pools on the surface, 2 to 3 minutes.
Add the pineapple and cook, stirring, until the liquid has almost dried up, about 2 minutes.
Add about 3/4 cup water and the sugar; bring to a boil.
Simmer until the pineapple is tender and the mixture thickens slightly, 5 to 6 minutes.
Taste and adjust for salt and sugar.
Add the fish and chile slices; reduce the heat to medium and cook, turning the fish once (take care not to break the pieces), 3 to 4 minutes, adding a little water if necessary, until fish is just cooked through.