Heat the vegetable oil in a large pot over medium heat. Add the diced onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and grated ginger, cooking for an additional 1-2 minutes until fragrant.
Add the red curry paste to the pot and mix well, cooking for another minute.
Pour in the coconut milk and vegetable broth, stirring to combine. Bring the mixture to a simmer.
Add the sliced carrots and diced bell pepper to the pot. Simmer for about 10 minutes until the vegetables are tender.
Stir in the baby spinach, soy sauce, and lime juice. Season with salt and pepper to taste.
While the soup simmers, prepare the dumplings. In a mixing bowl, combine the flour, baking powder, and salt.
Add the milk and melted butter, stirring until just combined. Do not overmix.
Drop spoonfuls of the dumpling batter into the simmering soup. Cover the pot and cook for an additional 10 minutes, allowing the dumplings to steam and cook through.
Serve hot, garnished with fresh herbs if desired.