Adjust rack to top position and preheat oven to 475 degrees. Wash and dry all produce. Trim and thinly slice scallions, separating whites from greens. Core, deseed, and dice green pepper. Quarter lime. Drain beans over a small bowl, reserving liquid.

Heat a drizzle of oil in a large pan over medium-high heat. Add green pepper and cook until just softened, 4-5 minutes.

Add scallion whites, Southwest Spice, half the beans, and 2 TBSP reserved bean liquid (you’ll use more later) to pan. Cook, stirring, until fragrant and warmed through, 2-3 minutes. Season with salt and pepper. Turn off heat.

Heat a large drizzle of oil in a small pot over medium-high heat. Add remaining beans and cook, stirring, until slightly softened, 2-3 minutes. Add 3 TBSP remaining reserved bean liquid (1/3 cup for 4 servings). Simmer until warmed through, 1-2 minutes. Lower heat and stir in 1 TBSP butter (2 TBSP for 4) and 1/2 tsp salt (1 tsp for 4). Turn off heat; mash with a potato masher or fork until mostly smooth. Season with pepper.

Spread tortillas with mashed beans. Place a small amount of filling on one half of each tortilla. Roll up tortillas, starting with filled side, and place seam side down in an 8-by-11- inch baking dish or ovenproof pan. (For 4 servings, assemble in a 9-by-13-inch baking dish or two smaller ones.) Pour enchilada sauce over to coat, then sprinkle with Mexican cheese. Bake until sauce is bubbly and cheese has melted, 5-7 minutes.

Meanwhile, in a second small bowl, combine sour cream and a squeeze of lime juice. Stir in water 1 tsp at a time until mixture reaches a drizzling consistency. Season with salt and pepper. Top enchiladas with crema and scallion greens. Divide between plates and serve with remaining lime wedges on the side.