Heat the macadamia oil in a large saucepan or Dutch oven over medium heat.
Add the sliced onion and cook for 5 minutes, stirring occasionally, until softened.
Stir in the grated ginger, cumin, coriander, and turmeric.
Cook for 1–2 minutes until fragrant.
Pour in the coconut milk and 200ml water.
Add the sweet potato cubes and stir well.
Bring the mixture to a gentle boil.
Reduce heat to medium-low.
Cover and simmer for 8–10 minutes until the sweet potatoes begin to soften.
Add the green beans.
Continue simmering for 2 minutes.
Stir in the zucchini and barramundi pieces.
Cover and simmer for 3–4 minutes, or until the fish is just cooked through and flakes easily.
Avoid stirring too vigorously to keep the fish intact.
Taste and adjust seasoning if needed.
Serve the One-Pot Fish Coconut Curry over steamed brown rice.
Garnish with lime wedges, sliced green chili, and fresh coriander sprigs.