Step 1

Heat oil in a large straight-sided skillet over medium-high heat. Add fennel, celery, and garlic and cook, stirring frequently, until tender and deep golden, about 8 minutes. Remove from heat.

Step 2

Meanwhile, bring a pot of generously salted water to a boil. Cook pasta according to package instructions. Reserve 1 cup pasta water; drain.

Step 3

Add pasta and pasta water to skillet with vegetables. Cook over medium-high heat, stirring to coat pasta, until warmed through, 2 to 3 minutes. Stir in fennel fronds, celery leaves, and lemon zest. Break up sardines into large pieces and gently fold into pasta. Season with salt and pepper and drizzle with oil.