Adjust oven rack to middle position and heat oven to 300 degrees. Line middle 6 cups of 12-cup nonstick muffin tin with paper or foil liners.

Stir almond flour, 2 teaspoons erythritol, and melted butter in bowl until combined. Divide almond mixture among prepared muffin cups and press into even layer using your fingers. Bake until crust is golden brown and set, 12 to 14 minutes. Transfer to wire rack and let cool while making batter.

Using stand mixer fitted with paddle, beat cream cheese and lemon zest on medium-high speed until light and fluffy, about 2 minutes. Reduce speed to low, add remaining ⅓ cup erythritol and salt, and mix until incorporated, about 1 minute, scraping down sides of bowl as needed. Add egg, vanilla, and lemon juice; increase speed to medium; and beat until smooth, about 1 minute.

Divide batter evenly among muffin cups. Bake until set, about 20 minutes. Let cheesecakes cool in muffin tin on wire rack for 30 minutes. Wrap muffin tin with plastic wrap and refrigerate until cheesecakes are chilled and firm, at least 1 hour. Serve.