Heat the olive oil in a dutch oven over medium-high heat. Add the carrots and onion and cook, stirring occasionally, for 4 minutes.
Add the garlic, serrano, cumin, and 1 tsp salt and cook until fragrant, about 15 seconds.
Pour in the vegetable broth and bring to a boil. Reduce heat to medium-low and simmer until carrots are tender, about 20 minutes depending on the size of your carrot slices.
Stir in the cilantro then transfer the soup, working in batches, to a blender and puree until smooth.
Return the pureed soup back into the dutch oven over medium low heat. Stir in the lime zest and heavy cream and cook until heated through. Season with salt and pepper to taste.