Bring a large pot of salted water to a boil and cook the pasta until just al dente, according to package instructions. Drain and set aside.
While the pasta cooks, season the salmon fillets with salt and pepper on both sides. Heat a tablespoon of olive oil in a large skillet over medium-high heat.
Place the salmon in the hot skillet skin-side down if applicable. Sear for about 4-5 minutes until golden brown and cooked halfway through, then flip and cook for another 2-3 minutes until fully cooked. Remove from pan and rest.
Add a tablespoon of butter and the minced garlic to the same skillet. Cook for about 30 seconds until fragrant, and the garlic turns slightly golden.
Add the cooked pasta to the skillet, tossing to coat it evenly in the garlic butter mixture. Zest the lemon directly over the pasta and give it a quick toss.
Chop or tear the spinach and add it to the skillet, stirring gently until it begins to wilt. Squeeze in half of the lemon juice for bright flavor.
Slice the rested salmon into thick pieces and gently fold them into the pasta along with any juices from resting. Warm everything together for another couple of minutes, allowing flavors to meld.
Taste and adjust seasoning with salt, pepper, and more lemon juice if desired. Serve immediately, garnished with extra lemon zest if you like.
