Preheat the oven to 220°. Line a half sheet pan (or other large baking sheet) with parchment paper or a silicone mat. If you don't have a large baking sheet, use 2 smaller ones to prevent the pans from getting overcrowded.
On the lined sheet pan, toss the asparagus pieces and gnocchi with the olive oil, lemon zest, and pepper. Spread everything out in a single layer.
Bake on the center rack of the preheated oven for 25 to 30 minutes, stirring about halfway through, until the asparagus is tender and the gnocchi is lightly browned.
In the meantime, prepare the dressing. Whisk together the olive oil, chopped tarragon, sliced scallion, lemon juice, Dijon mustard, garlic powder, salt, and pepper.
After removing the asparagus and gnocchi from the oven, drizzle the dressing over it. Stir until everything is coated. Serve, and enjoy!
