Mash together avocados, chipotle, red onion, lime juice, cilantro, salt, cumin with a fork until well-mixed. Stir in 2/3 cup of the toasted almonds and chopped tomato (if using) until combined. Garnish with the remaining toasted almonds.
Serve immediately, or cover the bowl with plastic wrap (so that the plastic is literally touching the entire top layer of the guacamole, to prevent any air getting in and browning the avocado) and refrigerate for up to 3 days.