Break the cauliflower into florets, removing the stems. Place the florets in the food processor bowl and pulse until the cauliflower looks like rice. This takes about 10 to 15 one-second pulses. You may need to do this in two batches to avoid overcrowding (which leads to mush).
Heat a large non-stick skillet over medium-high heat, about 3 minutes. Add the cauliflower bits, reduce the heat to low, cover with a lid, and let it gently cook for about 5 minutes, until just tender. Remove from heat and sprinkle with 1/4 teaspoon salt. Transfer to a medium bowl; add lemon juice and olive oil. Mix well and place in refrigerator to cool while you prep the rest of the ingredients.
While the cauliflower is cooling, prepare the other vegetables and herbs. Thinly slice the green and white parts of the scallion. Mince the chives. Coarsely chop the basil and parsley. Cut the peppers into eighths and the olives into quarters. Place everything in a large mixing bowl and toss with two wooden spoons to combine. Add the remaining 1/4 teaspoon salt, the black pepper, and 1 tablespoon olive oil. Toss again.
Remove the cauliflower from the fridge and mix with the veggies. Toss to combine, then return to the refrigerator to allow flavors to blend for about an hour. Can make ahead; lasts at least several days.