Heat oil in a saucepan over medium heat. Add onion. Cook, stirring, for 3 minutes or until softened. Add garlic, cumin and coriander. Cook, stirring, for 30 seconds or until fragrant. Add beans and 1/3 cup cold water. Cook, uncovered, for 5 minutes or until heated through. Remove from heat. Cool slightly.
Transfer mixture to a heatproof bowl. Using a potato masher, coarsely mash. Season with pepper.
Make guacamole: Using kitchen scissors, cut onion into thin slices. Place avocado in a bowl. Mash with a fork until smooth. Stir in lemon juice and onion. Season with salt and pepper. Serve.
Make tomato salsa: Combine tomato, cucumber and coriander in a bowl. Season with salt and pepper.
To assemble: Place corn chips on plates. Top with guacamole, refried beans and salsa.
