How to Make It
Preheat oven to 400°F. Line a baking sheet with parchment paper. Place plantain slices in a single layer on parchment; drizzle with 1 tablespoon of the oil, and sprinkle with 1⁄2 teaspoon of the salt. Roast in preheated oven until lightly browned and very tender, 16 to 18 minutes. Set aside.
Prepare rice according to package directions.
While rice and plantains cook, heat remaining 1 tablespoon oil in a saucepan over medium. Add jalapeño and 1 cup of the red onion; cook, stirring often, until tender, about 3 minutes. Stir in black beans, water, cumin, and remaining 1⁄2 teaspoon salt; cook until liquid is slightly reduced, 5 to 6 minutes.
Divide cooked rice evenly among 4 bowls. Top each with beans, roasted plantains, chopped radishes, and diced avocado. Sprinkle with chopped cilantro and remaining 1⁄4 cup red onion. Serve with lime wedges.