Finely slice the onions. Peel & grate the ginger. Peel the potatoes the cut into small cubes. Cut the cauliflower into florets.
Heat a spoonful of oil in a large pan and gently sauté the onions for 5 minutes. Add the ginger and curry paste. Stir until fragrant, then pour in the coconut milk and tomatoes. Add the cauliflower florets and the potato pieces.
Bring the boil then gently simmer for 20 to 30 minutes, until the vegetables are tender - don’t overcook them!
Turn off the heat. Season with salt and pepper, then stir in the lemon juice. Add the spinach and cover. Rest for 3 minutes until the spinach has wilted, then stir through and serve.