Guacamole — Avocado, lime, and nothing else it doesn't need

Rinse the finely diced onion in cold water for 30 seconds and drain. This removes the harsh sulfur compounds that otherwise dominate. Pat dry.

Halve the avocados and remove the pits. Scoop the flesh into a molcajete or wide bowl.

Add the salt and lime juice first, then mash with a fork or pestle until the texture is chunky — about 60–70% smooth with distinct pieces of avocado remaining. Do not work it to a purée.

Fold in the diced onion, serrano, and cilantro. Add the tomato last if using — fold gently to preserve its texture.

Taste and adjust: more salt if flat, more lime if lacking brightness, more serrano if the heat is not present. The guacamole should taste of avocado first, with bright lime and a clean serrano finish.

Serve immediately in the molcajete or transfer to a bowl. If not serving right away, press plastic wrap directly against the surface of the guacamole, pressing out all air pockets, and refrigerate for up to 2 hours.