Boil the pasta: Bring a large pot of salted water to a rolling boil. Cook pasta until al dente according to package directions. Reserve at least 1 cup of starchy pasta water before draining.

Warm the veggies: While pasta cooks, heat 2 tablespoons olive oil in a large skillet over medium. Add leftover grilled asparagus and any other grilled veggies. Cook 2–3 minutes, just to warm through and revive the charred edges. Transfer to a plate.

Build the sauce: In the same skillet, add 1 tablespoon olive oil and the butter. Add garlic and red pepper flakes. Cook 30–60 seconds until fragrant, not browned. Stir in lemon zest.

Emulsify: Add 1/2 cup reserved pasta water and squeeze in the juice of 1 lemon. Bring to a gentle simmer so the liquid looks slightly glossy.

Toss with pasta: Add drained pasta to the skillet and toss to coat. If it looks dry, splash in more pasta water a few tablespoons at a time until silky.

Add veggies back: Fold in the warmed grilled asparagus and other veggies. Toss gently so the tips don’t break. Season with salt and black pepper.

Cheese and herbs: Off the heat, sprinkle in parmesan and most of the herbs. Toss until the cheese melts into the sauce. Taste and adjust with more lemon juice, salt, or pepper.

Finish and serve: Drizzle with a little more olive oil. Top with extra parmesan, remaining herbs, and optional add-ins like toasted pine nuts or a handful of arugula for freshness.