Place the asparagus in a baking pan. Don’t worry about finding a pan large enough to hold the asparagus in one layer – the stalks can overlap a bit. Drizzle the olive oil over them and toss gently to coat the asparagus evenly. Sprinkle on the salt, and toss again.
Roast the asparagus for 8 to 10 minutes for thin stalks, 10 to 14 for thick ones. If they overlap, just give them a little shuffle with a spatula halfway through the cooking time so they all have a chance to brown a bit. Remember that they will continue to cook a bit after you remove them from the oven, so take them out while they’re still a little firmer than you would like.
While the asparagus are roasting, blend together the crème fraiche with the pesto, taste and see if it needs additional salt and pepper. (Remembering that you seasoned the asparagus.)
When the asparagus are cooked you can either drip over the thick creamy sauce, or you can transfer it to a small plastic bag, snip off a little corner of the bag and squeeze out the sauce over the asparagus. Serve just like that, sprinkled with lemon zest, or toss the asparagus so that it is coated with the sauce, and then sprinkle the lemon zest over.
Notes
You can use the same pesto I used, or another pesto of your choice, like Mint Basil Pesto, Caper-Olive Pesto, Nut-Free Basil Pesto with Pecorino Romano or Kale Pesto Recipe. Or, use a nice store-bought pesto. The Spinach Parsley Pesto is pretty mild, and other pestos based on stronger herbs will have more potent flavor, so start with a tablespoon mixed with ¼ cup crème fraiche and add more as desired.