In a large pot, bring the water and a healthy pinch of salt to a boil over high heat. Add the pasta and cook, stirring occasionally, until al dente, 6 to 8 minutes.
While the pasta cooks, put the salmon in a small bowl and douse it with the lemon juice.
Drain the pasta and transfer it to a medium bowl. Add the salmon, dill, crème fraîche, olive oil, capers, a pinch of salt, and a grind of pepper. Toss with tongs to combine well. Taste and adjust the seasoning, if desired. Serve warm.