Beat the cream cheese and sugar in a large bowl with a mixer on medium speed until fluffy, about 2 minutes. Beat in the lemon juice and vanilla. Beat in the heavy cream on high speed until stiff peaks form, 2 to 3 minutes. Spread the mixture on top of the pumpkin pie. Refrigerate until set, 1 to 2 hours.
Melt the cranberry sauce and 1 tablespoon water in a small saucepan over low heat, stirring until smooth, about 5 minutes. Mix the cornstarch with the remaining 1 tablespoon water in a small bowl, then whisk into the cranberry sauce. Bring to a simmer and cook just until thickened, about 30 seconds. Scrape into a bowl and let cool slightly, about 15 minutes. Spread over the cream cheese topping and refrigerate until set, about 30 minutes.