Cut the onion in half and add one half with tomatoes, bell peppers, and scotch bonnet peppers to blender with water and puree until smooth (about two minutes).
Meanwhile, add oil to pot over medium flame. Dice the remaining onion, chop the spinach, and mince or crush the garlic then add the onion to the heated oil along with curry powder, crushed maggi cube, smoked paprika, white pepper, ginger, and thyme. Do not add salt (see recipe notes).
Cook until fragrant and onions are nearly translucent (about four minutes) then add garlic and cook one minute more.
Stir the tomato paste into the pot, followed by the tomato puree and bay leaf. Reduce heat to medium low, cover, and cook for about 20 minutes or until bubbling and slightly reduced.
Stir in the broth or stock then increase heat to medium high and bring to a boil.
Taste test the sauce and add salt, if needed, to your preference. Reduce the heat to medium then add spaghetti to the pot and cook to al dente (about 16 minutes).
Remove from heat and discard bay leaf then stir chopped spinach into pasta until wilted. Serve hot.