Heat oil in medium saucepan over medium-high heat. Add onions; cook until soft and translucent, about 7 minutes. Stir in jalapeno pepper, garlic and cumin; cook until fragrant, about 30 seconds more. Add beans and their liquid to saucepan; bring bean mixture to a boil. Using potato masher, submersion blender or fork, mash beans until broken. Cook, stirring constantly until mixture is thick, about 5 minutes.
To assemble burritos, mound ½ cup rice, ½ cups bean mixture, ¼ cup cheese, 2 tbsp. corn, 1 tbsp. chopped scallions and 1 tsp. cilantro on one side of tortilla. Roll up tortilla into burrito shape (see below). Place burrito, seam-side down on serving plate or platter. Repeat with remaining ingredients.
Serve burritos with guacamole, pico de gallo, salista and sour cream, if desired.