Preheat oven to 325˚F.
Whip erythritol and lemon zest until incorporated.
Add ricotta, eggs, salt, almond flour, vanilla, limoncello (or lemon extract mix), and lemon juice. Mix until smooth and creamy.
Line a 9” springform pan with parchment paper and spray with non-stick cooking spray.
Bake for 90 minutes or until the center is set.
Turn off oven, crack the oven door open, and leave the cake in for 30-45 minutes.
Remove, allow to come to room temperature for 2 hours, wrap, and refrigerate for 4 hours or overnight.
Slice and serve.