Wash and halve the avocados: Rinse the avocados under cool water, then halve each one by running your knife lengthwise around the pit. Twist the two halves in opposite directions until they separate.
Remove the pit: Lodge your knife blade into the pit and twist to lift it out, or skip the blade and simply squeeze the sides of that half until the pit pops free.
Scoop the avocado: While the flesh is still sitting in the skin, slide a spoon right along the skin's edge to release it in one clean scoop. Transfer to a large mixing bowl.
Mash the avocado: Using a fork or pastry cutter, press against the sides of the bowl rather than stirring vigorously, stopping well before it's smooth — those uneven chunks are what give the guac its rustic texture. Halfway through, add the 1/4 teaspoon sea salt and half the 1 lime, juiced and zested; this softens the avocado while keeping it from browning.
Add the aromatics: Add the chopped Roma tomatoes, red onions, diced jalapeño, grated garlic, fresh cilantro, and the remaining lime juice, zest, and 1/4 sea salt to the bowl.
Fold and taste: Gently fold everything together, taking care not to overmix into a paste. Taste, and adjust with more lime juice, salt, or jalapeño as needed.
Serve: Transfer to a serving bowl and top with a bit of extra chopped tomato, onion, jalapeño, and cilantro.