Heat up olive oil. Once heated add onion and garlic until translucent.
Add beetroot and apple. Stir to combine. Add ¾ of the thyme leaves and stir again.
Pour broth into the soup pot and bring to boil. Put the lid on the pot, reduce heat to low and let simmer for 20-25 minutes.
Once the beetroot has softened blend to a silky smooth soup with a submersion blender. You can also use a regular blender, but you'll have to let the soup cool off first.
Optional: mix yogurt, lemon zest + juice and remaining thyme.
To serve, divide soup over soup bowls and swirl 1-2 tbsp of yogurt mixture in each bowl.