While the beans are cooking, peel and finely slice the onions. Heat olive oil in a large pan over medium-low heat. Add the onions and cook, stirring occasionally, until they become soft, golden brown, and caramelized. This will take about 20-30 minutes, so be patient and stir occasionally to prevent burning. Once caramelized, add the paprika and tomato paste, stirring to incorporate. Let the onions cook for another 2-3 minutes, adding a splash of water.