Preheat the oven to 475 degrees Fahrenheit (245 degrees Celsius). Line a baking sheet with foil and place it on a rack near the top of the oven, about 6 inches away from the heating element.
Cook the rice according to the package instructions.
Make the spice paste by mixing the brown sugar, curry powder, onion powder, garlic powder, kosher salt, and olive oil in a small bowl.
Place the salmon fillets skin-side down on the prepared baking sheet. Rub the spice paste over the top of the salmon fillets.
Bake the salmon for 6-12 minutes, depending on the thickness of the fillets and your desired level of doneness.
While the salmon is baking, heat the olive oil in a pan over medium heat. Add the garlic, ginger, and lemongrass, and saute for 5 minutes.
Add the brown sugar and red curry paste, and saute for 3 minutes.
Pour in the coconut milk and season with fish sauce, lime juice, and lime zest to taste. Stir in the spinach until it is wilted.
Once the salmon is cooked, place the fillets over the cooked rice and pour the coconut curry sauce over the top.
Garnish with fresh herbs, such as cilantro, basil, or mint, and enjoy!