Combine rice, 290ml water, 1 teaspoon avocado oil, and a pinch of salt in a small heavy-duty pot; bring to a boil. Cover, reduce heat to low, and simmer for 30 minutes or until almost all the liquid is absorbed. Remove from heat and let sit, covered, for 10 more minutes. Fluff with a fork and set aside.
Preheat the oven to 200°c. Line a rimmed baking tray with parchment paper and set aside. In a medium bowl, combine cauliflower florets and garlic cloves with 2 tablespoons of oil, toss to coat. Arrange in a single layer on the baking tray, season with salt and pepper, and roast until the cauliflower is tender and golden brown, 20-25 minutes, flipping halfway through. Transfer to a bowl and set aside.
Preheat the grill to medium-high heat for about 5 minutes. Line the same baking tray with a fresh piece of parchment paper; set aside.
Evenly coat salmon fillets with remaining 2 teaspoons of oil and arrange on the prepared baking tray. Sprinkle tops evenly with chilli powder; season with salt and pepper. Grill in the centre of the oven for 13-15 minutes or until salmon is cooked through.
Divide salmon fillets between two bowls and arrange artfully along with black rice, roasted cauliflower, orange wedges, and jalapeño (if using). To serve, drizzle with juice from orange wedges.
