Place walnuts in a dry skillet over medium heat. Stir frequently for 3–5 minutes until fragrant and lightly browned. Remove from heat and set aside.Tip: Watch closely—walnuts burn fast and will taste bitter if over-toasted.
Cook the Pasta
Bring a large pot of salted water to a boil. Cook tagliatelle until al dente according to package instructions.
Reserve ½ cup of pasta water before draining.
Prepare the Walnut Cream Sauce
In a large skillet, melt butter over low to medium heat.
Stir in the heavy cream gradually, keeping the heat gentle.
Puree half the toasted walnuts in a blender or food processor until smooth, then stir into the cream.Tip: Add cream slowly and stir constantly to prevent the sauce from separating.
Combine Pasta & Sauce
Add drained tagliatelle directly to the skillet with the sauce.
Toss to coat evenly, adding a little reserved pasta water if needed to reach a silky consistency.
Add Flavor Boosters
Stir in grated Parmesan, lemon zest, and juice. Taste and adjust salt and pepper.
Toss again until everything is well incorporated.Tip: Add lemon at the end to keep its bright, fresh flavor without curdling the cream.
Finish & Serve
Plate the pasta, sprinkle with the remaining toasted walnuts and chopped parsley for color and texture. Serve immediately.
Notes
I like to have some Parmesan on the table for those who want more.