Add onions and carrots and cook 3-5 minutes to soften.
Stir in garlic and ginger and cook 1 minute.
Add cumin, turmeric, coriander, cayenne and split peas. Heat until fragrant, 30 seconds.
Add soup stock and bring to boil. Reduce heat, cover with lid slightly askew and simmer until peas and vegetables are tender, 45 minutes. Stir occasionally.
Remove from heat and carefully puree until smooth, adding water if needed.