Spinach and Cauliflower Dahl

Name: Spinach and Cauliflower Dahl
Ingredients: 1 medium head of cauliflower, washed and cut into florets; 1 cup dried red lentils, washed and drained; 1 can coconut milk (400 ml); 1 medium onion, peeled and sliced; 2 cloves garlic, minced; 2 to 3 cups stock or water (depending on how thick you want it to be); 4 cups baby spinach, washed; ½ lemon or 1 lime, juiced; 2 tablespoons coconut oil; 2 teaspoons curry powder; 1 teaspoon nigella seeds or cumin seeds (cumin powder works too); pinch of cayenne (optional); salt and pepper, to taste