Line a skillet with a thin layer of water and sauté onion over high heat until translucent and most of the water has cooked off. Add cumin, chili powder and paprika, stirring to coat the onion, then add beans with their juices and stir to combine. Reduce heat to low and mash beans well using a fork or potato masher. It will look very soupy-don't be alarmed. Crank the heat up to high and bring to a boil. Once boiling, reduce heat to medium and simmer for 10 minutes. If the beans start popping and splashing, cover for a few minutes, then uncover. Stir every minute or so, scraping along the bottom to lift beans. After 10 minutes, the liquid should have significantly reduced. It's alright if it's still a little soupy-it will thicken as it cools. However, if it's really soupy, cook longer. Add salt and pepper to taste, then serve.