In a large pot over medium heat, bring 3 quarts of heavily salted water to a rolling boil. Have a large bowl of ice water ready on the side.
Add the broccolini and cook until bright green and tender, about 2 to 3 minutes (depending on the size of the broccolini). Quickly drain the water and place the broccolini in the ice bath to stop the cooking process. When the broccolini is cool remove them from the ice bath and place on a paper towel- lined plate.
Preheat the broiler to high with a rack set in the top third of the oven. In a medium bowl toss the broccolini in olive oil and garlic to coat then arrange in a single even layer on a baking sheet.
Sprinkle with red pepper flakes and sea salt. Broil until the tips of the broccolini start to char but are not burnt, about 5 to 6 minutes. Remove from the broiler and place back in the bowl.