• Peel and thinly slice the yellow onion.
• Pat the salmon dry with a paper towel. Cut into 1½-inch pieces; season generously with salt and pepper.
• Zest the lime and juice half for the curry, keeping the zest and juice separate; cut half into wedges for garnish.
• Remove the stem, ribs, and seeds from the red bell pepper; coarsely chop the pepper.
• Trim the root end from the bok choy; cut in half lengthwise, then coarsely chop.

In a large sauce pot over medium heat, warm 2 to 3 teaspoons oil until hot but not smoking. Add the onion and lemongrass curry paste, season lightly with salt and pepper, and cook, stirring occasionally, until fragrant, 2 to 3 minutes. Add the coconut milk and ½ cup water and bring to a boil, scraping up any browned bits from the bottom of the pot. Reduce to a simmer and add the salmon, lime zest, and 1 teaspoon lime juice. Cook, stirring occasionally, until the salmon begins to turn opaque, 1 to 2 minutes.
Add the bell pepper and bok choy, cover, and cook until the salmon is cooked through and the vegetables are just tender, 3 to 5 minutes. Remove from the heat and season to taste with salt and pepper.
While the curry cooks, prepare the cauliflower “rice.”

In a large frying pan over medium heat, warm 2 to 3 teaspoons oil until hot but not smoking. Add the cauliflower “rice” and cook, stirring occasionally, until the cauliflower starts to soften, 3 to 5 minutes. Remove from the heat and stir in the fried shallots, if using. Season to taste with salt and pepper.
While the cauliflower cooks, prepare the remaining garnishes.

• Coarsely chop the cashews.
• Strip the basil leaves from the stems; coarsely chop the leaves.

Transfer the cauliflower “rice” to individual bowls and top with the curry. Garnish with the cashews, basil, and lime wedges.