Adjust rack to top position and preheat oven to 425 degrees. Wash and dry all produce. Trim and thinly slice scallions, separating whites from greens. Heat a drizzle of oil in a small pot over medium-high heat. Add scallion whites; cook 1 minute. Stir in rice and 3/4 cup water (11/2 cups for 4 servings). Bring to a boil, then cover and reduce heat to low. Cook until rice is tender, 15-18 minutes. Keep covered off heat until ready to serve.

While rice cooks, drain pineapple over a small bowl, reserving juice; roughly chop. Trim green beans. Zest and quarter lime (for 4 servings, zest 1 lime; quarter both). In a separate small bowl, combine pineapple, scallion greens, 2 TBSP pineapple juice (3 TBSP for 4), a squeeze of lime juice, and lime zest to taste. Season with salt and pepper.

Toss green beans on a baking sheet with a drizzle of oil, salt, and pepper. Roast on top rack until browned and tender, 12-15 minutes.

While green beans roast, pat barramundi dry with paper towels; season all over with salt and pepper. Season flesh sides with half the Southwest Spice (use all for 4 servings); rub to evenly coat.

Heat a large drizzle of oil in a large pan over medium-high heat. Add barramundi skin sides down. Cook until skin is crispy, 4-5 minutes. (TIP: Lower heat if skin begins to brown too quickly.) Flip and cook until fish is opaque and cooked through, 2-3 minutes. Remove pan from heat.

Fluff rice with a fork; stir in 1 TBSP butter (2 TBSP for 4 servings), a squeeze of lime juice, and as much remaining lime zest as you like. Season with salt and pepper. Divide rice, barramundi, and green beans between plates. Top fish with salsa. Serve with remaining lime wedges on the side.