Preheat your oven to 400°F (200ºC).
Season salmon fillets with kosher salt and black pepper, place in a baking dish, and bake for about 12 minutes.
Cook pappardelle pasta according to package instructions until al dente.
Melt unsalted butter in a medium pot, add minced garlic, sauté for 2 minutes, then add heavy cream, lemon zest, and grape juice; cook until slightly thickened.
Add cooked pasta, spinach, and capers to the cream sauce, then gently flake in the baked salmon.
Toss everything together and serve immediately while hot.