Pour coconut milk, alcohol- free vanilla, stevia powder and salt into a small bowl. Whisk until stevia and salt have dissolved and set aside.
Add mashed avocados, lime zest and juice into a food processor and mix until smooth. Blend in the coconut milk mixture and process until thoroughly combined. With the food processor running pour in the melted coconut oil.
Apply the tart filling into the prepared tart crust. Spread it evenly and refrigerate for 1 to 2 hours.
The tart can be stored in the refrigerator for up to 2 days. Serve with toasted coconut flakes.