Step 1: Prepare the Avocados
Cut avocados in half lengthwise around the pit. Twist the halves apart. Carefully remove the pit by tapping it with the heel of your knife and twisting. Scoop the avocado flesh into a medium bowl using a spoon.

Step 2: Mash the Avocados
Add lime juice immediately to the avocados (this prevents browning). Using a fork or potato masher, mash the avocados to your desired consistency. For traditional guacamole, leave it slightly chunky – not completely smooth. Mash about 80% of the avocado, leaving some small chunks for texture.

Step 3: Add Aromatics
Add the diced red onion, chopped cilantro, diced jalapeño (if using), minced garlic, salt, cumin (if using), and black pepper to the mashed avocado. Stir everything together with a spoon until well combined.

Step 4: Add Tomatoes (Optional)
If using tomatoes, gently fold them in last. This prevents them from making the guacamole watery. Make sure tomatoes are well-drained by patting them with a paper towel before adding.

Step 5: Taste and Adjust
Taste the guacamole and adjust seasonings as needed. Add more lime juice for brightness, more salt for flavor enhancement, more jalapeño for heat, or more cilantro for freshness. The key is balancing all flavors so nothing dominates.

Step 6: Serve Immediately
Transfer guacamole to a serving bowl. If desired, garnish with extra cilantro, a drizzle of lime juice, or a few reserved avocado chunks on top. Serve immediately with tortilla chips, or cover tightly and refrigerate until ready to serve.

Step 7: Prevent Browning (If Storing)
If not serving immediately, press plastic wrap directly onto the surface of the guacamole, eliminating air pockets. This prevents oxidation and browning. Refrigerate up to 2 days.