In a sauce pain, combine chopped onion with 1 tablespoon water and cook on medium heat until onion is softened.
Add 2 cups of beans and mash with potato masher. Add remaining unmashed beans and heat through or about 5 minutes.
Combine the masa and water in a bowl until dough holds together. Roll dough into 12 balls the size of golf balls. Flatten each ball on parchment paper and 1/4 inch think.
Heat a large skillet with oil over medium-high heat. When hot, add 2-3 sopes and cook for about 3-4 minutes on each side until slightly browned.
To serve, top each sope with the mashed bean mixture, chopped lettuce or cabbage, avocado, green onion and cilantro.