Combine all the ingredients except for the cauliflower, spinach, lime juice, and cilantro in the slow cooker.
2 cups red lentils, 14.5 ounces diced tomatoes, 1 onion, 1 teaspoon ground ginger, 4 cups vegetable broth, 2 tablespoons curry paste, ½ teaspoon ground coriander, ½ teaspoon cumin, ½ teaspoon cayenne pepper, 2 teaspoons sugar, 1 ½ teaspoons salt
Cook on low for 6 hours or high for 3-4 hours.
About 30 minutes before it's done, stir in the cauliflower, replace the cover and let it continue to cook.
12 ounces frozen cauliflower
Right before serving, stir in the spinach until it's wilted.
5 ounces fresh spinach
Add the lime juice and cilantro, mix well, and serve.
1 tablespoon lime juice, ¼ cup chopped cilantro
Notes
I bought a 10 ounce bag of spinach and then used about half of it.
If you can't find red lentils, you can use yellow lentils. Green or brown lentils don't have a similar texture after cooking so they aren't good substitutes. In a pinch, you can use pinto beans.
You can substitute chicken broth for the vegetable broth if desired.
To substitute curry powder instead of curry paste, use 2 teaspoons. You may need to adjust that amount to taste. To add a little extra heat, stir in some cayenne pepper.