Heat the oil in a large pot or dutch oven. Add in the diced onion and saute for 5 minutes or until translucent. Add in the minced garlic and grated ginger and saute an additional 5 minutes.
Add in the curry and tomato pastes and saute for 2 minutes.
Add in all remaining ingredients aside from the lime juice and kale.
Stir well to combine, then bring to a boil, reduce the heat to low, and let simmer, uncovered, for about 20 minutes or until the potatoes can be easily pierced with a fork.
Once the potatoes are soft, transfer about 1 cup worth of the curry to a blender and blend until creamy. This is optional, but it helps thicken the curry and give it a rich and creamy consistency.
Transfer back to the pot and stir well. Stir in the lime juice and spinach and let simmer until it wilts.
Garnish with fresh cilantro and red pepper flakes, serve over fresh white rice and enjoy!