Bring a large pot of water to a boil. Add a generous pinch of salt to season the pasta water.
Add the pumpkin ravioli and cook according to the package directions until just al dente. Drain carefully and set aside.
Meanwhile, heat a large dry skillet over medium heat. Add the chopped walnuts and toast for 2–3 minutes, stirring frequently until fragrant and lightly browned. Transfer to a plate.
Wipe the skillet clean and return it to medium heat. Add the butter and let it melt, bubble, and turn golden brown with darker flecks. Swirl the pan occasionally to prevent burning.
Stir the olive oil into the browned butter. Add the fresh sage leaves and cook for 2–3 minutes until crisp. Remove the leaves with tongs or a slotted spoon and chop or crumble them.
Add the cooked ravioli to the skillet and gently toss until coated in the sage brown butter. Season with flaked sea salt and freshly ground black pepper.
Sprinkle the toasted walnuts and crispy sage over the ravioli. Finish with a squeeze of fresh lemon juice and serve immediately
