This is a simple pasta centering on a single ingredient – the turnip, a member of the brassica family. Many brassicas are trendy. Over the past few years, I’ve noticed lots of kale, cauliflower and Brussels sprouts side dishes at restaurants in Brooklyn and Portland. No wonder. These vegetables take wonderfully to many forms of cooking, whether shredded raw in a salad, slow roasted and caramelized or baked until crisp. Battersby in Brooklyn won tons of press for its crispy kale in fish sauce last year, and recently I have seen variations on a whole roast cauliflower or cauliflower steak. But turnips are an untrendy brassica, a little more pungent and mustardy than kale or cauliflower. Not fair. Turnips roast perfectly brown, with a nice juiciness and just a hint of their raw bite. And they make a wonderful pesto — blend with a little olive oil and you will have a plenty rich dish without going overboard on the nuts or cheese.