Adjust rack to top position and preheat oven to 425 degrees. Wash and dry all produce. Dice sweet potato into 1/2-inch pieces. Halve, peel, and slice onion into 1/2-inch-thick wedges. Trim and thinly slice scallions, separating whites from greens. Dice tomato. Zest and quarter lime.

Toss sweet potato on one side of a baking sheet with a drizzle of oil, salt, pepper, and half the Southwest Spice (you’ll use the rest later). Toss onion on empty side of same sheet with a drizzle of oil, salt, and pepper. Roast on top rack, tossing halfway through, until veggies are browned and tender, 25 minutes.

Meanwhile, heat a drizzle of oil in a small pot over medium-high heat. Add scallion whites and cook until softened, 1 minute. Add rice, 3/4 cup water (11/2 cups for 4 servings), and a big pinch of salt. 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, in a small bowl, combine sour cream, a squeeze of lime juice, and a pinch of chipotle powder (taste and add more from there if you like things spicy). Stir in water 1 tsp at a time until mixture reaches a drizzling consistency. Season with salt and pepper.

Pat chicken dry with paper towels; season with salt, pepper, and remaining Southwest Spice. Heat a drizzle of oil in a large pan over medium-high heat. Add chicken and cook until browned and cooked through, 3-5 minutes per side. Transfer to a cutting board. Let chicken rest, then slice crosswise.

In a second small bowl, combine tomato, scallion greens, a squeeze of lime juice, salt, and pepper. Fluff rice with a fork; stir in 1 TBSP butter (2 TBSP for 4 servings), a squeeze of lime juice, lime zest to taste, salt, and pepper. Divide between bowls. Top with veggies, chicken, and salsa. Drizzle with chipotle crema. Serve with any remaining lime wedges on the side.