Preheat your oven to 160°C (320°F).
In a food processor, combine the crumbled digestive biscuits and melted butter. Process until the mixture resembles wet sand.
Press the biscuit mixture evenly into the base of the springform pan to form the crust. Place in the fridge while preparing the filling.
In a mixing bowl, combine the cooked beetroot, feta cheese, cream cheese, and lemon juice. Using a whisk, blend until smooth.
Add the eggs one at a time, mixing well after each addition. Season with salt and pepper to taste.
Pour the beetroot and cheese mixture over the chilled crust and smooth the top with a spatula.
Bake in the preheated oven for 60 minutes, or until the cheesecake is set and slightly jiggly in the center.
Once baked, turn off the oven and leave the cheesecake inside for another 10-15 minutes.
Remove from the oven and let it cool to room temperature before transferring to the fridge to chill for at least 2 hours or until completely cold.
Before serving, top with chopped pistachios for added crunch and decoration.