Prepare pasta al dente according to package directions.
In a medium saucepan melt butter and garlic until fragrant (about 1-2 minutes)
Add heavy cream, pumpkin puree, parmesan cheese, parsley, and red pepper flakes. Simmer over low heat until sauce thickens.
Remove from heat; season with salt and pepper. Sprinkle with grated or shredded parmesan cheese.