Trim, peel, and chop the onion; chop the garlic. Put the oil in a large pot over medium heat. Add the onions, garlic, and a pinch of salt and cook, stirring occasionally until they’re very soft and starting to turn golden, 5 to 10 minutes. Put the rice in a strainer and rinse under running water; drain. Drain and rinse the beans in a colander. Scrub, trim, and peel the beets; cut them into 1-inch chunks. Peel the banana.
Remove the pot from the heat and transfer the onion mixture to the bowl of a food processor or a blender. Add 1/2 the banana, about 1/3 of the beans, and 1/4 cup water and purée until smooth, adding water, a teaspoon at a time, if necessary to keep the machine running. Transfer the bean mixture to the pot and return it to medium-high heat. Add the remaining beans, the smoked paprika, and 1 1/2 cups water and bring to a boil.
Add the beets to the pot and adjust the heat so the mixture bubbles gently. Cover and cook, stirring occasionally until the beets are tender, 20 to 25 minutes. Taste and adjust the seasoning.
Put the rice, 1/2 the coconut milk (save the rest for another use), 1 cup water, and pinch of salt in a medium saucepan and bring to a boil. Lower the heat so it bubbles gently but steadily; cover and cook, undisturbed, until the rice is tender and the water is absorbed, 15 to 20 minutes. Remove the pan from the heat and leave it covered.
Rinse the cilantro and scallion; trim the toughest stems from the cilantro and chop it; chop the scallion. Put the cilantro and scallions in a medium bowl. Rinse, peel, and segment the oranges. Chop the oranges and remaining 1/2 banana into bite-sized pieces and add to the bowl. Quarter the lime. Squeeze one of the lime wedges over the salsa, sprinkle with salt and pepper, and stir; taste and adjust the seasoning. Fluff the rice with a fork. To serve, divide the rice among 2 bowls, ladle the stew over, and top with a spoonful of salsa and a lime wedge.