Arrange a rack in the middle of the oven and heat the oven to 425ºF.
Peel and trim 2 pounds parsnips. Halve each parsnip crosswise. Halve each bottom, thinner piece lengthwise. Halve the top pieces lengthwise, then cut lengthwise again into thirds or quarters so they are roughly the same size as the bottom pieces. Transfer the parsnips to a rimmed baking sheet.
Drizzle the parsnips with 2 tablespoons olive oil and season with ½ teaspoon kosher salt and ½ teaspoon black pepper. Toss until evenly coated, then spread out into a single, even layer.
Roast until starting to brown on the bottom, 20 to 25 minutes. Remove the parsnips from the oven. Sprinkle with 3 tablespoons dukkah or za’atar spice and toss until evenly coated. Spread back into an even layer.
Return the parsnips to the oven and roast until fork tender and the spices are fragrant, 5 to 10 minutes more.
