1. Peel the potatoes and chop them into medium-sized pieces, about 2.5 cm (1 inch) in size.

2. Divide the cauliflower into florets, making sure they are roughly the same size so they cook evenly.

3. In a large pot, melt 30g (2 tablespoons) of butter over medium heat. Add 1 medium onion, chopped, and 2 cloves of garlic, minced. Cook until the onion is translucent and the garlic is softened, about 5 minutes.

4. Add 475ml (2 cups) of water, 225g (1 cup) of crushed tomatoes, 475ml (2 cups) of vegetable broth, and 225g (1 cup) of lentils to the pot. Season with 1 teaspoon of ground cumin, 1/2 teaspoon of dried oregano, 1/2 teaspoon of salt, and 1/4 teaspoon of black pepper.

5. Bring the mixture to a boil, then reduce the heat to low and simmer, covered, for 20 minutes.

6. Add the chopped potatoes to the pot and continue to simmer, covered, for about 10 minutes, or until they are tender when pierced with a fork.

7. Add the cauliflower florets to the pot and cook, covered, for an additional 5 minutes, or until they are tender but still crisp.

8. Taste and adjust the seasoning as needed.

9. Serve the stew warm, garnished with a squeeze of lemon juice if desired.