Meanwhile, add the olive oil and smashed garlic to a small saucepan. Heat over low heat for 5 minutes to infuse the oil. Discard the garlic cloves.
Arrange the broccolini on a sheet pan and drizzle the garlic oil over the top. Toss to evenly coat the broccolini. Season with salt and pepper. Roast for 10-15 minutes.
Meanwhile, lightly toast the pistachios in a small skillet set over low heat. Remove from the heat when you can smell the nuts, approx. 3-4 minutes. Chop and set aside.
Transfer the broccolini to a serving platter and top with the chopped pistachios and the lemon zest.