In a pot, add salt, seasoning cube, curry, thyme, half of the chopped onion, and the gutted mackerel. Pour in enough water to cover and boil for 5 to 7 minutes. Remove the fish from the heat, let it cool, then remove the bones and break the fish into chunks.
In a frying pan over medium heat, add the cooking oil. Saute the remaining chopped onions, stirring often until they soften and become slightly translucent.
Add the chopped tomatoes and cook for 4 to 5 minutes, allowing the mixture to reduce and the flavors to deepen.
Season with salt, seasoning cube, and peppers. Stir well, then cook for 5 to 10 minutes, or until the oil begins to float on top of the sauce.
Add the fish pieces into the tomato sauce, mixing carefully so they don't fall apart.
Crack the eggs into a bowl, beat lightly, then pour into the pan. Let it sit for 1 to 2 minutes, then gently stir over low heat until the eggs are just set.
Remove from the heat. Avoid overcooking to keep the stew from drying out!