Step 1

Place a rack in middle of oven; preheat to 425°. Toss onion, garlic, tomatoes, gnocchi, 3 Tbsp. oil, and 1¼ tsp. Diamond Crystal or ¾ tsp. Morton kosher salt on a rimmed baking sheet to coat; season generously with pepper and toss again to combine.

Step 2

Roast, stirring once or twice, until gnocchi are golden and starting to crisp, most of the tomatoes have burst, and onion is golden, 25–30 minutes.

Step 3

Remove garlic from baking sheet, peel, and place in a small bowl. Mash with ¼ tsp. salt (garlic should be quite soft). Whisk in lemon juice and remaining 1 Tbsp. oil; season dressing with pepper and more salt if needed.

Step 4

Add arugula, basil, and Parmesan to baking sheet and drizzle dressing over; toss to combine. Divide among plates and drizzle with a little more oil.