Heat 1 tablespoon olive oil in a large skillet over medium heat.
Season salmon with salt and pepper, then sear for 2–3 minutes per side until golden and just cooked through.
Transfer to a plate and set aside (it’ll flake apart later).
In the same pan, add remaining olive oil and garlic.
Cook 30–60 seconds until fragrant.
Add red pepper flakes if using.
Add pasta, broth, water, lemon zest, and a big pinch of salt.
Bring to a boil, then reduce to a simmer for 5 minutes.
Add the asparagus directly into the pan.
Continue cooking until pasta is al dente and liquid has mostly absorbed, about 6-7 more minutes.
Toss occasionally with tongs so nothing sticks.
Stir in butter (or more olive oil) and lemon juice.
Add flaked salmon back to the pan, gently toss to coat in the sauce.
Season with extra salt, pepper, or lemon juice to taste.
Garnish with fresh parsley or basil and a drizzle of olive oil.
Optional: top with shaved Parmesan or feta if you want a bit of creaminess.