Fill a large pot with a few inches of water and fit it with a steamer attachment. Bring the water to a simmer. Transfer the broccolini to the steamer basket.
Steam the broccolini till crisp tender, 4-5 minutes. Remove the broccolini from the steamer and transfer it to a baking sheet or a large cutting board that's lined with a tea towel or paper towels. Pat the broccolini very dry. Allow it to cool for a few minutes on the towels.
Place the broccolini onto a serving dish (or in a storage container, if you're meal prepping). Dress it well with the tahini dressing; alternatively, plate portions of the broccolini and serve the tahini dressing table-side. Enjoy.