Heat a medium saute pan on medium heat. Add the chorizo and cook until golden in color, about 6 minutes. Remove the chorizo to a drain on a plate lined with some paper towels. Add the onions to the pan with the chorizo fat. Saute until the onions are translucent, about 4 minutes. Return the chorizo to the pan. Add the refried beans to the mixture. Continue cooking for about 5 minutes. Turn the heat off and reserve for tostadas and burritos.