Prepare the spice rub by whisking together demerara sugar, curry powder, garlic powder, and ground ginger in a bowl. Add water to create a thick paste. Preheat the oven to 190°C (375°F). Coat the salmon fillets with the spice mixture and place on a baking sheet. Bake for 6 minutes until beginning to turn opaque.

While salmon bakes, heat olive oil in a large skillet over medium heat. Sauté minced garlic and fresh ginger for about 3 minutes until fragrant. Add a bit of demerara sugar and Thai red curry paste, cooking until thickened slightly, about 1 minute. Stir in coconut milk, bringing to a gentle boil before simmering for 2 minutes.

Incorporate the chopped spinach into the coconut sauce, stirring until wilted and bright green, around 2-3 minutes. Keep the sauce warm on low heat.

Add partially cooked salmon fillets to the skillet. Cover and simmer for another 5-8 minutes until salmon flakes easily and is fully opaque.

To serve, mound rice on each plate, place salmon atop, and drizzle with coconut sauce. Garnish with chopped basil and coriander.