Preheat your oven to 160°C (320°F) and line the bottom of your springform pan with baking paper.
Cook the beetroots by boiling or roasting them until tender (about 30-40 minutes). Allow to cool, peel, and chop into small pieces.
In a food processor, combine the digestive biscuits and melted butter, blending until the mixture resembles wet sand. Press this mixture firmly into the base of the springform pan.
In a mixing bowl, combine the cooked beetroot, crumbled feta cheese, eggs, cream cheese, sour cream, sugar, vanilla extract, lemon juice, and a pinch of salt. Blend until smooth.
Pour the beetroot mixture over the crust in the springform pan and spread evenly with a spatula.
Bake in the preheated oven for about 40 minutes, or until the edges are set and the center has a slight jiggle.
Turn off the oven and leave the cheesecake inside for an additional 10 minutes. Remove from the oven and cool completely at room temperature.
Refrigerate the cheesecake for at least 4 hours (or overnight) to set fully.
Before serving, sprinkle crushed pistachios on top and garnish with whole pistachios.
Slice and enjoy your Beetroot Feta Cheesecake!