Preheat a gas or charcoal grill to a moderately hot temperature, about 375°F; if using coals, wait until they turn white-hot.
In a large mixing bowl, stir together the oil, garlic, crushed red pepper, half the lemon juice, and some salt and pepper to taste; add the calamari, stirring to coat.
When the grill is ready, spread out the calamari on the grill and cook, turning a few times, until just firm and lightly charred, 4-5 minutes.
Remove the calamari from the grill to another large mixing bowl; add the tomato, remaining lemon juice, parsley, and some salt and pepper to taste. Toss to combine.
Divide between bowls and serve straight away for best results.
