Here's a simple recipe to make mission-style burritos at home.
Place tortillas, wrapped in foil, in an oven preheated to 350°.
Meanwhile, sauté onions in cooking oil in a medium-sized saucepan until translucent. Stir in pinto beans and cook until desired it reaches the desired temperature.
Remove tortillas from the oven. Portion the beans, steak, cheese, guacamole, sour cream, and salsa evenly in the center of each tortilla.
To assemble, first fold one half of the tortilla until it covers the filling. Take the adjacent sides and fold them over the first fold. Holding the three folded sides taught, and wrap the fourth corner tightly over the other three.