Bring a large pot of water to a boil. Season with salt. Add pasta and cook until al dente according to package directions. Drain and reserve 1 cup of pasta cooking water.
While pasta cooks, transfer milk to a small pot. Bring to a simmer over medium heat. Reduce to low and keep warm until needed.
Heat a large sauté pan over medium high heat. Pat salmon dry and season with salt and pepper. Add 1 tablespoon of oil to pan, followed by the salmon. Cook for approximately 4-5 minutes per side, or to desired doneness. Transfer to a plate and set aside.
Reduce heat to medium. Add remaining 2 tablespoons of oil to the pan, followed by the sliced onions. Season with salt and pepper. Sauté approximately 5 minutes or until softened and translucent. Add garlic and sundried tomatoes and sauté 30-60 seconds.
Stir in chickpea flour and cook for 1-2 minutes. Slowly pour in warmed milk, stirring constantly to prevent lumps.
Add cooked pasta and baby spinach to pan along with a few tablespoons of pasta water, as needed, to thin the sauce. Toss to combine.
Break salmon into large chunks and gently stir into pasta.
Stir in lemon juice. Taste and adjust seasoning, as needed.
Notes
Cook the pasta al dente to prevent it from becoming too soft when mixed with the sauce.
Use fresh salmon fillets for the best texture and flavor, avoiding pre-cooked or canned options.
Stir in the salmon gently to avoid breaking it into small pieces.
If the sauce becomes too thick, gradually add reserved pasta water or a splash of milk to loosen it.