Adjust rack to top position and preheat oven to 425 degrees. Wash and dry all produce. Dice sweet potato into ½-inch pieces. Halve, peel, and cut onion into ½-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, half the Southwest Spice (you’ll use the rest later), salt, and pepper. Toss onion on empty side 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; cook until softened, 1 minute. Add rice, ¾ cup water (1½ 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 remaining Southwest Spice, salt, and pepper. 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 5 minutes (while making salsa in next step), 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; add a squeeze of lime juice, salt, pepper, and lime zest to taste. (TIP: If you like, stir in 1 TBSP butter; 2 TBSP for 4 servings.) Divide rice between bowls; top with veggies, chicken, and salsa. Drizzle with chipotle crema. Serve with any remaining lime wedges on the side.