For homemade guacamole for 4 people:
1. Using a molcajete (Mexican mortar and pestle) or a fork grind together the white onion, jalapeño and 1 tbsp of cilantro to form a paste.
2. Peel and dice the avocado. Combine with the chili paste.
3. Add tomato, salt, remaining cilantro and lime juice. Mix and serve immediately.