Preheat the oven to 375°. Line a rimmed baking sheet with foil. Arrange the salmon fillets, skin side down on the baking sheet and season with salt and pepper. Lay the lemon slices on the fillets, overlapping them slightly. Roast the salmon for about 12 minutes, until just cooked through.
Meanwhile, in a small bowl, combine the lemon juice and shallot and let stand for 10 minutes. Whisk in the olive oil and tarragon and season with salt and pepper.
Transfer the salmon to plates. Spoon the tarragon vinaigrette on top and serve.