Place the macadamias in a bowl, cover with 2 cups of cold water and soak for between 8 and 24 hours.
Drain and rinse the macadamias and place in a food processor.
Add 1 tablespoon of the lemon juice and process as finely as possible. If you prefer, use a blender. Add remaining lemon juice to taste. If nuts appear dry, add up to 3 tablespoons of boiling water to create desired consistency.
Allow to stand for 1 hour before serving. Store refrigerated for up to 1 week.
For the soup:
Preheat oven to 180°C. Trim each beetroot at the leafy end and individually wrap in aluminium foil. Place on a baking tray and roast for 40 minutes, until a skewer or sharp knife meets no resistance and the beetroot are tender.
Remove from foil and cool slightly before rubbing off the skin. Chop the beetroots into pieces.
Heat the oil in a large saucepan. Add the onion and cook over a medium heat for about 5 minutes, until golden. Add the stock and beetroot and bring to the boil. Reduce heat and simmer for 10 minutes. Using a hand-held blender or food processor, blend until smooth.
Heat a large heavy-based frying pan over medium heat. Add the caraway, pumpkin and sesame seeds. Cook for 4-5 minutes, tossing occasionally, until caraway is aromatic.
Remove from heat and stir through the macadamias.
Serve warm beetroot soup topped with macadamia sour cream and macadamia and seed sprinkles.