Because fresh corn can vary in sweetness, we’ve called for seasoning with a range of lime juice. To make this dish spicier, reserve and add the chile seeds.
Heat 1 tablespoon oil in 12-inch nonstick skillet over medium heat. Add onion, pepper, and jalapeño; cook, stirring occasionally, until onion is softened, 4 to 6 minutes. Add garlic, cumin, and ¼ teaspoon salt and cook until fragrant, about 1 minute. Add beans and cook until warmed through, about 1 minute. Transfer black bean mixture to large bowl and wipe out skillet.
Heat remaining 1 tablespoon oil in now-empty skillet over medium-high heat until shimmering. Add corn and sprinkle with ½ teaspoon salt. Cook, without stirring, until corn is browned on bottom and beginning to pop, about 3 minutes. Stir and continue to cook, stirring once or twice, until corn is spotty brown all over, 2 to 3 minutes longer. Transfer corn to bowl with black bean mixture.
Stir in cilantro and 2 tablespoons lime juice. Season with salt and remaining lime juice to taste. Serve.
